feat: adapt to DSH 0.1.7-alpha.1 and yield the read-only previews

DSH 0.1.7-alpha.1 is 1299 commits past 0.1.6-alpha.2 and rewrites four
contracts this plugin was built on. The peer floor moves to
^0.1.7-alpha.1 (semver's prerelease rule means ^0.1.6-alpha.2 can never
match a 0.1.7 prerelease); 0.1.6-alpha.2 and earlier stay on v0.19.1.
Released as 0.21.0-alpha.1 (dist-tag alpha).

Hard breaks:
- dsh-settings was rewritten: register(ns, schema) is gone, a form is
  addressed by the plugin row's Loader entry id and read from the
  module's exported Config. The preferences are merged into Config and
  marked volatile — which requires DSH's own schemastery, because only
  that build wraps a volatile field in the cosmokit reference the
  loader's volatile commit walks. With the public package a settings
  write reports success and revision 1 while the effective value never
  changes.
- ui-primitives renamed its whole icon family (IconXxx14/16 ->
  IconXxxRegular/Medium): 26 imported symbols, 17 files. The failing
  mode is render-time, not load-time. Five call sites that relied on the
  old 14px default now pass size={14} explicitly.
- Session format v4 rejects source.kind === 'plugin'; the side-chat
  boundary injection now writes plugin:dsh-better-sidebar, the same kind
  DSH's own v3->v4 migration produces, so historical threads survive.
  Tool results moved to role 'tool' with top-level content/isError; all
  four parsers accept both shapes.
- The client session snapshot dropped subagentsByParent/jobsBySession
  and the on-demand subagent-catalog observation API. The Tasks page
  reads projectionsBySession and a new jobs.list route.

Yields and convergence:
- The read-only previews go to DSH's documentpreview (Office->PDF, a
  spreadsheet worker, zoom, per-directory refresh); editor.canOpen
  refuses those 26 extensions. Markdown, HTML (with its sandbox
  switches) and the editable code buffer stay.
- The host browser kind is desktop-profile-only now, so the web e2e
  lanes expect no browser entry and assert its absence.
- Link takeover claims only urlTarget links and passes the rest to the
  host, fixing a regression from the 0.1.6 round: the fallback pointed
  at a 'browser' type the plugin no longer registers, so http links in
  its own markdown did nothing.

Also fixed, found along the way:
- The file tree refreshes live (new directory watch over the plugin's
  own socket), since the plugin owns the `files` kind.
- ctx.sessions.list has no `current` field at either tag; the three
  readers were dead. They now use ctx.sidebarRight.mounted.
- package.json.files was missing lib/client-locale.js.
- Two genuinely dead call sites: sessions.openSubagent/open/
  refreshSubagents do not exist on the current baseline, so the
  topology click, the jump-back and the retry were all no-ops.
- The test harness window shim lacked addEventListener, which the 0.1.7
  primitives call at module-evaluation time; and the e2e token exchange
  needs Playwright's request stack, not Node's fetch.

tests/e2e/mount.e2e.ts

@@ -58,16 +58,22 @@ const SEEDED_README_FILE = 'readme-style.md'
 const CRASH_STRIP_PATTERNS = [/^dsh-better-sidebar:/, /^\[dsh-better-sidebar\]/]
 
 /**
- * The tab types the plugin itself contributes, plus the host-owned kinds the
+ * The tab types the plugin itself contributes, plus the host-owned kind the
  * guide is asserted to still offer.
  *
- * `terminal` and `browser` are DSH 0.1.6's own right-Sidebar types: this
- * plugin deliberately ships neither (it used to own both), so the guide must
- * show exactly ONE entry for each when the host mounts those packages — a
- * second entry would mean the plugin is shadowing the host again.
+ * `terminal` is DSH's own right-Sidebar type: this plugin deliberately ships
+ * neither terminal nor browser (it used to own both), so the guide must show
+ * exactly ONE `terminal` entry when the host mounts that package — a second
+ * entry would mean the plugin is shadowing the host again.
+ *
+ * `browser` is deliberately NOT in this list and is asserted ABSENT below: DSH
+ * 0.1.7 disables `@deepseek-ai/dsh-client-ui-sidebar-browser` outside the
+ * desktop profile ("Web profiles opt in; Desktop retains sandboxed HTTP(S)
+ * Browser tabs"), and every lane here drives the web profile. Listing it would
+ * demand a guide entry the host itself has stopped offering.
  */
 const PLUGIN_TABS = ['files', 'git', 'subagent', 'sidechat'] as const
-const HOST_OWNED_TABS = ['terminal', 'browser'] as const
+const HOST_OWNED_TABS = ['terminal'] as const
 const NATIVE_TABS: readonly string[] = [...PLUGIN_TABS, ...HOST_OWNED_TABS]
 
 let api: APIRequestContext
@@ -298,6 +304,15 @@ test('plugin mounts into the DSH shell and survives a built-in tab sweep', async
     ).toHaveCount(1)
   }
 
+  // The browser kind the plugin handed to the host is NOT offered on a web
+  // profile: DSH 0.1.7 mounts its browser package only for the desktop
+  // profile. Pinned rather than merely omitted, so a future lane that starts
+  // seeing a browser entry learns the host changed its mind.
+  await expect(
+    page.locator('[data-sidebar-right-guide-entry="browser"]'),
+    'the web profile must not offer a browser guide entry at DSH 0.1.7',
+  ).toHaveCount(0)
+
   // Sweep every type through the guide. Each open mounts a real viewer (the
   // editor and mermaid chunks arrive lazily); a failure anywhere surfaces as a
   // pageerror or a crash strip, both of which the next assertion sees. A pane