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.

src/client/SideChatView.tsx

@@ -29,16 +29,16 @@ import clsx from 'clsx'
 import {
   ConnectionIndicator,
   DiffBlock,
-  IconApiOutline14,
-  IconBrowseOutline16,
-  IconChevronRightOutline14,
-  IconEditOutline16,
-  IconNewChatOutline16,
-  IconPlusOutline16,
-  IconSearchOutline16,
-  IconSendOutline14,
-  IconSparkle16,
-  IconStopFill16,
+  IconApiOutlineRegular,
+  IconBrowseOutlineRegular,
+  IconChevronRightOutlineRegular,
+  IconEditOutlineRegular,
+  IconNewChatOutlineRegular,
+  IconPlusOutlineRegular,
+  IconSearchOutlineRegular,
+  IconSendOutlineRegular,
+  IconSparkleRegular,
+  IconStopFillRegular,
   MarkdownText,
   Menu,
   ReadBlock,
@@ -198,7 +198,7 @@ function CollapsibleRow(props: {
         )}
       >
         <span className={css.sidechatRowChevron}>
-          <IconChevronRightOutline14 size={12} />
+          <IconChevronRightOutlineRegular size={12} />
         </span>
         {leading}
         {label}
@@ -239,19 +239,19 @@ function toolLeading(name: string, failed: boolean): React.ReactNode {
   switch (name) {
     case 'bash':
     case 'pwsh':
-      return <IconApiOutline14 size={14} />
+      return <IconApiOutlineRegular size={14} />
     case 'read':
     case 'web_fetch':
-      return <IconBrowseOutline16 size={14} />
+      return <IconBrowseOutlineRegular size={14} />
     case 'edit':
     case 'write':
-      return <IconEditOutline16 size={14} />
+      return <IconEditOutlineRegular size={14} />
     case 'grep':
     case 'glob':
     case 'web_search':
-      return <IconSearchOutline16 size={14} />
+      return <IconSearchOutlineRegular size={14} />
     default:
-      return <IconSparkle16 size={14} />
+      return <IconSparkleRegular size={14} />
   }
 }
 
@@ -596,7 +596,7 @@ export function SideChatView(props: {
 
   const menuItems = useMemo<MenuEntry[]>(() => {
     const items: MenuEntry[] = [
-      { id: '$new', label: t('sideChatNew'), icon: <IconPlusOutline16 /> },
+      { id: '$new', label: t('sideChatNew'), icon: <IconPlusOutlineRegular /> },
     ]
     if (threads.length > 0) {
       items.push({ type: 'separator', id: '$sep' })
@@ -677,7 +677,7 @@ export function SideChatView(props: {
     return (
       <div className={css.sidechat}>
         <div className={css.sidechatHero}>
-          <IconNewChatOutline16 />
+          <IconNewChatOutlineRegular />
           <div
             className={clsx(
               css.sidechatHeroTitle,
@@ -793,7 +793,7 @@ export function SideChatView(props: {
               disabled={busy !== null}
               title={t('sideChatCancelTitle')}
             >
-              <IconStopFill16 />
+              <IconStopFillRegular />
             </button>
           ) : (
             <button
@@ -804,7 +804,7 @@ export function SideChatView(props: {
               disabled={composer.trim() === '' || busy !== null}
               title={t('sideChatSend')}
             >
-              <IconSendOutline14 size={16} />
+              <IconSendOutlineRegular size={16} />
             </button>
           )}
         </div>