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/changes/ops.ts

@@ -74,6 +74,8 @@ function pathOf(args: Record<string, unknown>): string | undefined {
 interface ToolResultMessageLike {
   source?: { kind?: unknown; callId?: unknown }
   content?: unknown
+  /** The 0.1.7 first-class tool message lifts the error flag onto the message. */
+  isError?: unknown
 }
 
 /** One 'tool-result' content block (inner blocks carry the text). */
@@ -83,33 +85,46 @@ interface ToolResultBlockLike {
   isError?: unknown
 }
 
-/** The finalized plain text of one tool result (inner text blocks joined). */
-function resultText(message: ToolResultMessageLike): string | undefined {
+/**
+ * The result blocks and error flag of one tool/result message, read under BOTH
+ * logged shapes: 0.1.6 wrapped the result in a single `type: 'tool-result'`
+ * content block on a user-role message (the text nested inside it, `isError`
+ * on the wrapper), 0.1.7's first-class tool-role message carries the blocks at
+ * the message's own top level with `isError` lifted onto the message.
+ * Historical logs keep the old shape forever, so both are read. Undefined when
+ * the message carries no block array.
+ */
+function resultOf(message: ToolResultMessageLike): { blocks: readonly unknown[]; isError: boolean } | undefined {
   if (!Array.isArray(message.content)) return undefined
-  const parts: string[] = []
   for (const block of message.content) {
     if (block === null || typeof block !== 'object') continue
-    const candidate = block as ToolResultBlockLike
-    if (candidate.type !== 'tool-result') continue
-    const inner = candidate.content
-    if (!Array.isArray(inner)) continue
-    for (const item of inner) {
-      if (item === null || typeof item !== 'object') continue
-      const textItem = item as { type?: unknown; text?: unknown }
-      if (textItem.type === 'text' && typeof textItem.text === 'string') parts.push(textItem.text)
+    const wrapper = block as ToolResultBlockLike
+    if (wrapper.type !== 'tool-result') continue
+    return {
+      blocks: Array.isArray(wrapper.content) ? wrapper.content as readonly unknown[] : [],
+      isError: wrapper.isError === true,
     }
   }
+  return { blocks: message.content as readonly unknown[], isError: message.isError === true }
+}
+
+/** The finalized plain text of one tool result (its text blocks joined). */
+function resultText(message: ToolResultMessageLike): string | undefined {
+  const blocks = resultOf(message)?.blocks
+  if (blocks === undefined) return undefined
+  const parts: string[] = []
+  for (const item of blocks) {
+    if (item === null || typeof item !== 'object') continue
+    const textItem = item as { type?: unknown; text?: unknown }
+    if (textItem.type === 'text' && typeof textItem.text === 'string') parts.push(textItem.text)
+  }
   return parts.length > 0 ? parts.join('\n') : undefined
 }
 
-/** Whether a tool result reported an error (the inner block's isError flag). */
+/** Whether a tool result reported an error (0.1.7's message-level flag, else
+ *  the 0.1.6 wrapper block's flag). */
 function resultIsError(message: ToolResultMessageLike): boolean {
-  if (!Array.isArray(message.content)) return false
-  return message.content.some((block) => {
-    if (block === null || typeof block !== 'object') return false
-    return (block as ToolResultBlockLike).type === 'tool-result'
-      && (block as ToolResultBlockLike).isError === true
-  })
+  return resultOf(message)?.isError === true
 }
 
 /**