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/prefs-shared.ts

@@ -22,13 +22,6 @@ export interface SidebarPrefs {
    * conversation (any new job id, not just the first one).
    */
   autoOpenJobs: boolean
-  /**
-   * Whether the model-facing agent terminal tools (terminal_create / list /
-   * send / read / wait_for / resize / signal / close) are injected into the
-   * model's toolset. Off by default: the feature stays dormant until the
-   * user explicitly enables it in the side card settings.
-   */
-  agentTerminalTools: boolean
   /**
    * Whether the model-facing `sidebar_open` tool is injected into the
    * model's toolset — one tool that lets the model actively open a local
@@ -37,25 +30,6 @@ export interface SidebarPrefs {
    * dormant until the user explicitly enables it in the side card settings.
    */
   agentOpenTools: boolean
-  /**
-   * Custom terminal font-family stack (a CSS font-family value, e.g.
-   * `'JetBrains Mono', monospace`). Empty string follows the app's theme
-   * monospace font (`--ds-font-family-code`). Applied live to every
-   * terminal tab; configured under the terminal card's secondary settings.
-   */
-  terminalFontFamily: string
-  /**
-   * Custom terminal font size in px (9–32). Applied live to every terminal
-   * tab; configured under the terminal card's secondary settings.
-   */
-  terminalFontSize: number
-  /**
-   * Whether expanding the bottom panel for the FIRST time in a session tries
-   * to open a fresh terminal tab there (the terminal quota/type still gates
-   * the attempt). On by default; the switch lives under the terminal tab's
-   * row in the Side card settings.
-   */
-  bottomPanelAutoTerminal: boolean
   /**
    * Whether the editor tab runs in merged mode: a path input replaces the
    * plain header and a toggleable file-tree panel (with a global name
@@ -79,21 +53,6 @@ export interface SidebarPrefs {
    * one-click global off + retry.
    */
   workspaceFence: boolean
-  /**
-   * The shell the UI and agent terminals spawn (absolute path or bare
-   * executable name). Empty (default) keeps the legacy resolution order:
-   * `cordis.patch.yml` `config.shell`, then `$SHELL` / login shell /
-   * `powershell.exe` on Windows. Set it from the terminal card's gear in
-   * the Side card settings (or the yaml) to pin a specific shell — takes
-   * effect for terminals opened afterwards.
-   */
-  terminalShell: string
-  /**
-   * Explicit arguments for `terminalShell`, space-separated (empty keeps
-   * the platform defaults; when set, they fully replace them — same
-   * contract as the yaml `shellArgs`).
-   */
-  terminalShellArgs: string
   /**
    * Title-bar / shell compatibility scheme (the "位置兼容模式" setting):
    * - `auto` (default): CONSERVATIVE — only the standard Window Controls
@@ -151,50 +110,30 @@ export interface SidebarPrefs {
    * restore for the current file.
    */
   htmlViewerDefaultUnsafe: boolean
-  /**
-   * Whether the browser tab drops its sandboxed iframe. Sandbox ON (the
-   * default) keeps browsed sites in an opaque origin with no GUI access;
-   * turning it OFF runs any visited site with the GUI's own origin — it
-   * can read session data and act as the logged-in GUI. Only for trusted
-   * sites; the setting copy warns.
-   */
-  browserNoSandbox: boolean
   /**
    * MASTER switch: whether clicking an EXTERNAL link in the GUI (chat
    * messages, tool rows, prose mentions) is taken over into the sidebar at
    * all. On by default; the per-protocol granularity lives in
    * `browserInterceptHttp` / `browserInterceptHttps` (the protocol flag
-   * must also be on), and the target tab's own enable switch gates it too.
-   * Ctrl/Cmd+click always bypasses the takeover. Kept as the master so old
+   * must also be on). Ctrl/Cmd+click always bypasses the takeover. Kept as the master so old
    * documents keep their meaning with no migration (an explicit `false`
    * stays "never take over").
    */
   browserInterceptLinks: boolean
   /**
-   * Whether clicking an http EXTERNAL link in the GUI opens the sidebar
-   * (the built-in browser tab, or a plugin tab that declares `urlTarget`)
-   * instead of a new browser tab. On by default; gated on the
-   * `browserInterceptLinks` master and the target tab's own enable switch.
+   * Whether clicking an http EXTERNAL link in the GUI opens DSH's own
+   * sidebar browser (or a plugin tab that declares `urlTarget`) instead of a
+   * new browser tab. On by default; gated on the `browserInterceptLinks`
+   * master.
    */
   browserInterceptHttp: boolean
   /**
    * Whether clicking an https EXTERNAL link in the GUI opens the sidebar
    * instead of a new browser tab. OFF by default — most https sites (e.g.
    * GitHub) refuse iframe embedding, so the system browser is the smoother
-   * default; gated on the `browserInterceptLinks` master and the target
-   * tab's own enable switch.
+   * default; gated on the `browserInterceptLinks` master.
    */
   browserInterceptHttps: boolean
-  /**
-   * Comma-separated allowlist of local (loopback) authorities the browser
-   * tab may navigate to — `localhost`, `127.0.0.1`, `127.0.0.1:5174`, or
-   * host:port pairs. Empty by default: loopback addresses stay blocked so a
-   * browsed page cannot probe local services. Each entry is either a bare
-   * hostname (all ports) or host:port; the GUI's own origin is always
-   * allowed regardless. The iframe sandbox still renders allowed local
-   * pages in an opaque origin, exactly like any other site.
-   */
-  browserAllowedLoopback: string
   /**
    * Per-tab enable switches, keyed by tab descriptor id (`'explorer'`,
    * `'my-plugin:db'`). An ABSENT key means enabled — only an explicit
@@ -223,11 +162,6 @@ export interface SidebarPrefs {
   pluginSettings: Record<string, Record<string, unknown>>
 }
 
-/** Range contract of {@link SidebarPrefs.terminalFontSize}. */
-export const TERMINAL_FONT_SIZE_MIN = 9
-export const TERMINAL_FONT_SIZE_MAX = 32
-export const TERMINAL_FONT_SIZE_DEFAULT = 13
-
 /** Range contract of {@link SidebarPrefs.titleBarStripPx}. */
 export const TITLE_BAR_STRIP_MIN = 0
 export const TITLE_BAR_STRIP_MAX = 120
@@ -241,15 +175,9 @@ export type TitleBarScheme = typeof TITLE_BAR_SCHEMES[number]
 export const SIDEBAR_PREFS_DEFAULTS: SidebarPrefs = {
   autoOpenSubagent: true,
   autoOpenJobs: true,
-  agentTerminalTools: false,
   agentOpenTools: false,
-  bottomPanelAutoTerminal: true,
-  terminalFontFamily: '',
-  terminalFontSize: TERMINAL_FONT_SIZE_DEFAULT,
   editorExplorer: false,
   workspaceFence: true,
-  terminalShell: '',
-  terminalShellArgs: '',
   titleBarScheme: 'auto',
   titleBarPresetId: '',
   customCss: '',
@@ -257,21 +185,14 @@ export const SIDEBAR_PREFS_DEFAULTS: SidebarPrefs = {
   titleBarStripPx: TITLE_BAR_STRIP_DEFAULT,
   htmlViewerNoSandbox: false,
   htmlViewerDefaultUnsafe: false,
-  browserNoSandbox: false,
   browserInterceptLinks: true,
   browserInterceptHttp: true,
   browserInterceptHttps: false,
-  browserAllowedLoopback: '',
   tabsEnabled: {},
   viewersEnabled: {},
   pluginSettings: {},
 }
 
-/** Clamp one terminal font size into the contract range (shared by schema and client reads). */
-export function clampTerminalFontSize(value: number): number {
-  return Math.min(TERMINAL_FONT_SIZE_MAX, Math.max(TERMINAL_FONT_SIZE_MIN, Math.round(value)))
-}
-
 /** Clamp one title-bar strip height into the contract range (shared by schema and client reads). */
 export function clampTitleBarStrip(value: number): number {
   return Math.min(TITLE_BAR_STRIP_MAX, Math.max(TITLE_BAR_STRIP_MIN, Math.round(value)))