feat: yield the terminal and browser to DSH 0.1.6's own sidebar types

DSH 0.1.6-alpha.2 ships a right-Sidebar terminal and a right-Sidebar browser
of its own. Both were things this plugin had built from scratch, so keeping
them meant two implementations of one surface plus a plugin that shadows a
host type the product is actively developing.

Terminal: the plugin's whole PTY stack goes — the UI-tab manager, the
agent-owned registry, the lazy node-pty loader, the eight model-facing
terminal_* tools, the xterm view and its font/link/scrollback helpers, and
the cross-session 'pinned terminal' rail that existed only to keep a terminal
alive across a session switch. The host's terminal kind becomes the only
provider, which also retires the node-pty dependency, its pnpm allowBuilds
entry, and the installer's -Repair mode (issue #140's whole class of
'node-pty failed to load' support).

Model-facing capability note: the plugin used to inject terminal_* tools
(off by default). Those are the model's only cross-call persistent terminal,
and DSH's own equivalent (@deepseek-ai/dsh-tool-terminal) is not mounted by
any shipped bundle, so removing them leaves the model with the one-shot
bash/pwsh tools only. That is the accepted cost of not maintaining a second
PTY surface; the README documents how to enable the upstream toolset.

Browser: the plugin's browser tab type is dropped, so the host's own browser
kind owns embedded pages. The DOM-level link takeover STAYS (it is the only
thing that can route an https link to the system browser by protocol, which
the host does not do) but now delegates to the host's browser tab via
ctx.sidebarRight.openTab('browser', …) with a window.open fallback, and the
two settings that only ever configured the plugin's own iframe (sandbox
escape hatch, loopback allowlist) go with it — along with the host-side
browser.probe route they fed.

Cards: the empty-pane welcome cards adopt the host's guide-capsule recipe
(0.5px l4 hairline, 24px radius, layer-1 fill, 56px floor, 14px/20px padding)
so the plugin's 'pick what opens here' surface reads as the same design as
DSH's own. A theme.spec guard pins the geometry and the token-only paint —
including that the upstream-only --dsw-alias-bg-l1/-l2 spellings (defined
nowhere, so their declarations are silently dropped upstream) never appear
here.

Also drops the dead state the removed features left behind (SidebarTab.pin,
nextTerminal, agentWaits, bottomOpenedOnce, the agent-tab helpers, the
pinned-tab memo key), re-points every test fixture that used them at
surviving equivalents, and prunes the specs of the deleted features.

src/client/builtins/index.ts

@@ -8,7 +8,7 @@
  */
 import type { Context } from '../../context-types.ts'
 import type { BetterSidebarService } from '../service.ts'
-import { builtinTabs, type BuiltinTabOptions } from './tabs.tsx'
+import { builtinTabs } from './tabs.tsx'
 import { builtinViewers } from './viewers.tsx'
 
 /**
@@ -20,10 +20,9 @@ import { builtinViewers } from './viewers.tsx'
 export function registerBuiltins(
   ctx: Context,
   service: BetterSidebarService,
-  options: BuiltinTabOptions = {},
 ): () => void {
   const disposers: (() => void)[] = []
-  for (const tab of builtinTabs(ctx, options)) {
+  for (const tab of builtinTabs()) {
     disposers.push(service.registerTab(tab))
   }
   for (const viewer of builtinViewers()) {

src/client/builtins/tabs.tsx

@@ -1,86 +1,34 @@
 /**
- * The 7 built-in tab descriptors: the plugin registers its own pages
- * (editor / git — the unified changes tab / subagent / sidechat / terminal /
- * browser / diff) through
+ * The built-in tab descriptors: the plugin registers its own pages
+ * (editor / git — the unified changes tab / subagent / sidechat / browser /
+ * diff) through
  * the same {@link BetterSidebarService} external plugins use — eating its
- * own dogfood. The terminal descriptor owns its quota (`TERMINAL_LIMIT`)
- * and mints `terminal:<uuid>` ids through `createTab`; the browser mints
- * `browser:<n>` the same way (no quota). The editor IS the files window
- * (the old standalone explorer merged into it).
+ * own dogfood. The editor IS the files window (the old standalone explorer
+ * merged into it).
+ *
+ * DSH 0.1.6-alpha.2 ships its own right-Sidebar terminal and browser tab
+ * types, so this plugin contributes neither: the host's `terminal` kind owns
+ * interactive shells outright, and the host's `browser` kind (delegated to
+ * from the chat's http(s) links) owns embedded pages. See
+ * docs/plans/2026-09-21-dsh-0.1.6-alpha.2-adaptation.md.
  */
 import { IconCodeOutline16, IconPanelLeftOutline16 } from '@deepseek-ai/dsh-client-ui-primitives'
-import type { Context } from '../../context-types.ts'
 import {
-  browserTabIcon, changesTabIcon, filesTabIcon, sidechatTabIcon, tasksTabIcon, terminalTabIcon,
+  changesTabIcon, filesTabIcon, sidechatTabIcon, tasksTabIcon,
 } from './tab-icons.tsx'
-import { allLeaves, isAgentTabId, type SidebarState } from '../state.ts'
 import { t } from '../locales.ts'
 import { openSidebarFile } from '../sidebar-file.ts'
 import { EditorHost } from '../EditorHost.tsx'
 import { OpenWithSettings } from '../open-with-settings.tsx'
-import { lazyChunkComponent } from '../lazy-chunk.tsx'
 import { ChangesTab, opCountOf } from '../changes/ChangesTab.tsx'
 import { DiffTab } from '../DiffTab.tsx'
 import { SubagentView } from '../SubagentView.tsx'
 import { consumeSidechatSeed, SideChatView, sidechatThreadIdOf } from '../SideChatView.tsx'
 import { api } from '../api.ts'
-import { BrowserView } from '../BrowserView.tsx'
-import { TERMINAL_FONT_SIZE_MAX, TERMINAL_FONT_SIZE_MIN } from '../../prefs-shared.ts'
-import type { ComponentType } from 'react'
-import type { SessionScope } from '../api.ts'
-import type { SidebarStore } from '../state.ts'
 import type { TabDescriptor } from '../service.ts'
 
-/**
- * Lazy wrapper over the terminal view: xterm (and its stylesheet) is fetched
- * only when a terminal tab is first opened (see chunk-loader.ts). The
- * wrapper keeps the descriptor contract `(props) => ReactNode` — Sidebar
- * calls it as a plain function.
- *
- * TerminalView's props are { scope, tabId, store } — `tabId` is NOT part of
- * TabComponentProps (it carries `tab: SidebarTab` instead), so the
- * descriptor maps it explicitly; a bare pass-through would leave tabId
- * undefined and TerminalView's isAgentTabId(tabId) would crash on
- * `undefined.startsWith` (regression-pinned in tests/lazy-chunk.spec.tsx).
- */
-const LazyTerminal = lazyChunkComponent<TerminalViewProps>(
-  'terminal',
-  (mod) => mod.TerminalView as ComponentType<TerminalViewProps> | undefined,
-)
-
-/** The terminal view's props (mirror of TerminalView's own signature). */
-interface TerminalViewProps {
-  scope: SessionScope
-  tabId: string
-  store: SidebarStore
-}
-
-/** How many UI-owned terminals may be open at once (agent-owned ones are uncapped). */
-export const TERMINAL_LIMIT = 3
-
-/** Optional per-registration builtin behavior (currently terminal title). */
-export interface BuiltinTabOptions {
-  /** Returns the display title for newly opened terminal tabs. */
-  terminalTitle?: () => string
-}
-
-/** A client-side uuid for terminal tab identity (not shown in the UI). */
-function terminalUuid(): string {
-  if (typeof crypto !== 'undefined' && typeof crypto.randomUUID === 'function') {
-    return crypto.randomUUID()
-  }
-  return `t${Date.now().toString(36)}${Math.random().toString(36).slice(2)}`
-}
-
-/** Count UI-owned terminals (agent:` tabs excluded — they are the model's). */
-function uiTerminalCount(state: SidebarState): number {
-  return allLeaves(state.bottomSplits)
-    .flatMap(leaf => leaf.tabs)
-    .filter(tab => tab.type === 'terminal' && !isAgentTabId(tab.id)).length
-}
-
 /** The 6 built-in tab descriptors. */
-export function builtinTabs(ctx: Context, options: BuiltinTabOptions = {}): readonly TabDescriptor[] {
+export function builtinTabs(): readonly TabDescriptor[] {
   return [
     {
       id: 'editor',
@@ -246,116 +194,6 @@ export function builtinTabs(ctx: Context, options: BuiltinTabOptions = {}): read
         <SideChatView ctx={ctx} scope={scope} tab={tab} visible={visible} />
       ),
     },
-    {
-      id: 'terminal',
-      title: () => t('terminal'),
-      description: () => t('guideDescTerminal'),
-      icon: terminalTabIcon,
-      order: 40,
-      available: (_ctx, _scope, state) => uiTerminalCount(state) < TERMINAL_LIMIT,
-      // Declarative settings: the model-facing terminal tools switch, the
-      // bottom-panel first-expansion auto-terminal switch, and the custom
-      // font family/size rows render under this card in the Side card
-      // settings page (the host gates the toolset on the tools one
-      // independently; the font rows apply live to every terminal).
-      settings: {
-        toggles: [{
-          key: 'agentTerminalTools',
-          title: () => t('settingsToolsTitle'),
-          desc: () => t('settingsToolsDesc'),
-        }, {
-          key: 'bottomPanelAutoTerminal',
-          title: () => t('settingsBottomTerminalTitle'),
-          desc: () => t('settingsBottomTerminalDesc'),
-        }, {
-          key: 'terminalShell',
-          type: 'text',
-          title: () => t('settingsShellTitle'),
-          desc: () => t('settingsShellDesc'),
-          placeholder: t('settingsShellPlaceholder'),
-        }, {
-          key: 'terminalShellArgs',
-          type: 'text',
-          title: () => t('settingsShellArgsTitle'),
-          desc: () => t('settingsShellArgsDesc'),
-          placeholder: t('settingsShellArgsPlaceholder'),
-        }, {
-          key: 'terminalFontFamily',
-          type: 'text',
-          title: () => t('settingsFontFamilyTitle'),
-          desc: () => t('settingsFontFamilyDesc'),
-          placeholder: t('settingsFontFamilyPlaceholder'),
-        }, {
-          key: 'terminalFontSize',
-          type: 'number',
-          title: () => t('settingsFontSizeTitle'),
-          desc: () => t('settingsFontSizeDesc'),
-          min: TERMINAL_FONT_SIZE_MIN,
-          max: TERMINAL_FONT_SIZE_MAX,
-          unit: 'px',
-        }],
-      },
-      createTab: (state) => {
-        const count = uiTerminalCount(state)
-        if (count >= TERMINAL_LIMIT) return null
-        return {
-          tab: {
-            id: `terminal:${terminalUuid()}`,
-            type: 'terminal',
-            title: options.terminalTitle?.() ?? t('terminal'),
-          },
-          // Keep the legacy counter advancing for compatibility with older
-          // persisted states; new ids no longer use it.
-          patch: { nextTerminal: state.nextTerminal + 1 },
-        }
-      },
-      component: ({ tab, scope, store }) => <LazyTerminal scope={scope} store={store} tabId={tab.id} />,
-    },
-    {
-      id: 'browser',
-      title: () => t('browser'),
-      description: () => t('guideDescBrowser'),
-      icon: browserTabIcon,
-      order: 50,
-      // Declarative settings: the sandbox escape hatch, the link-takeover
-      // MASTER switch, and the per-protocol takeover switches (http on /
-      // https off by default) render under this tab's row in the Side card
-      // settings page (the sandbox one is warned on).
-      settings: {
-        toggles: [{
-          key: 'browserNoSandbox',
-          title: () => t('settingsBrowserSandboxTitle'),
-          desc: () => t('settingsBrowserSandboxDesc'),
-        }, {
-          key: 'browserInterceptLinks',
-          title: () => t('settingsBrowserLinksTitle'),
-          desc: () => t('settingsBrowserLinksDesc'),
-        }, {
-          key: 'browserInterceptHttp',
-          title: () => t('settingsBrowserHttpTitle'),
-          desc: () => t('settingsBrowserHttpDesc'),
-        }, {
-          key: 'browserInterceptHttps',
-          title: () => t('settingsBrowserHttpsTitle'),
-          desc: () => t('settingsBrowserHttpsDesc'),
-        }, {
-          key: 'browserAllowedLoopback',
-          type: 'text',
-          title: () => t('settingsBrowserLoopbackTitle'),
-          desc: () => t('settingsBrowserLoopbackDesc'),
-          placeholder: t('settingsBrowserLoopbackPlaceholder'),
-        }],
-      },
-      createTab: (state) => ({
-        tab: {
-          id: `browser:${state.nextBrowser}`,
-          type: 'browser',
-          title: t('browser'),
-        },
-        patch: { nextBrowser: state.nextBrowser + 1 },
-      }),
-      component: (props) => <BrowserView {...props} />,
-    },
     {
       id: 'diff',
       title: () => t('changes'),