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.

scripts/e2e-aggregate-mount.sh

@@ -108,14 +108,16 @@ if grep -q "duplicate prefix route" "$ERR_LOG" "$OUT_LOG" 2>/dev/null; then
   die "检测到 duplicate prefix route（双挂载未退让）"
 fi
 
-# 真实方法探活：terminal.deps 是插件自己的 handler（writeOk → HTTP 200 +
-# {"ok":true,...}）。成功响应证明至少一个实例真正注册了 /sidebar/api 路由
-# ——generic missing-route 404 无法冒充（P2: Probe a real sidebar API method）。
-DEPS="$(curl -s -X POST "$URL/sidebar/api/terminal.deps" 2>/dev/null || true)"
-if ! printf '%s' "$DEPS" | grep -q '"ok":true'; then
-  die "/sidebar/api/terminal.deps 未返回 ok:true（响应：$(printf '%s' "$DEPS" | head -c 200)）"
+# 真实方法探活：settings.get 是插件侧栏卡偏好的读取端（writeOk → HTTP 200 +
+# {"ok":true,...}；未挂 settings 服务的部署也照回 ok，值取缺省）。选它当哨兵
+# 的理由：/sidebar/api 是插件自己 fence 的 prefix 路由，未注册的方法统统 404，
+# 所以 {"ok":true} 只可能来自插件真实注册的 handler —— generic missing-route
+# 404 无法冒充（P2: Probe a real sidebar API method）。
+RESP="$(curl -s -X POST "$URL/sidebar/api/settings.get" 2>/dev/null || true)"
+if ! printf '%s' "$RESP" | grep -q '"ok":true'; then
+  die "/sidebar/api/settings.get 未返回 ok:true（响应：$(printf '%s' "$RESP" | head -c 200)）"
 fi
-say "/sidebar/api/terminal.deps → ok:true（真实 handler 存活）"
+say "/sidebar/api/settings.get → ok:true（真实 handler 存活）"
 
 STATUS="$(curl -s -o /dev/null -w '%{http_code}' -X POST "$URL/sidebar/api/__e2e_unknown__" 2>/dev/null || true)"
 say "/sidebar/api POST 未知方法 → HTTP ${STATUS}（期望 404）"

scripts/package-registry.mjs

@@ -31,8 +31,6 @@ const files = [
   'lib/client-registry.js.map',
   // Lazy chunks: the client fetches these from the host's /sidebar/bundle
   // route on first use (see src/client/chunk-loader.ts / src/bundle-route.ts).
-  'lib/client-terminal.js',
-  'lib/client-terminal.js.map',
   'lib/client-editor.js',
   'lib/client-editor.js.map',
   'lib/client-mermaid.js',