feat: workspaces own their sessions; desktop parity; sidebar and settings cleanup

Workspace sessions (docs/plans/desktop-parity, phases 1-5 and 7):
- sessions.lane_id: a workspace lists only the sessions its panes held,
  stamped by bindRunSession (first writer wins, nested `claude -p`
  excluded); GET /api/sessions?lane=&archived=
- session row state dot, double-click rename, archive (sessions.archived_at,
  hides only); the activity bar's duplicate Sessions tab removed
- Fork beside Resume (--fork-session, Claude only), Ctrl/Cmd+click a live
  session opens it in a second pane, a diff line's comment is pasted into
  the workspace's last-focused pane (lib/panePaste.ts)

dashboard_runs stability:
- a pane's previous run is archived as <pane>@<started_at> instead of being
  overwritten by INSERT OR REPLACE
- a run is flagged abandoned only once its tmux session is gone, at boot and
  on the run-heal beat (panes outlive a server restart)

UI:
- sidebar: no footer, language or theme block; small collapse button in the
  brand corner; version + update check in the connection details modal, a
  status-bar dot while a release is out; language in Settings -> General
- one Switch component for every switch, the themed Checkbox for every
  checkbox (no native checkboxes)

Also: AI Tools catalog trimmed to 10 built-ins (custom-file prompt modes
tested through fixtures), and the workspace plans under docs/plans/ (the
multi-user server plan lives in the AgentHub-Server repo).

server/lib/pty-run.js

@@ -106,6 +106,7 @@ function buildClaudeArgv({
   permissionMode,
   effort,
   resumeSessionId,
+  forkSession = false,
   initialPrompt,
   addDirs = [],
   systemPromptFile = null,
@@ -129,6 +130,9 @@ function buildClaudeArgv({
   if (model) argv.push("--model", model);
   if (effort && EFFORT_LEVELS.has(effort)) argv.push("--effort", effort);
   if (resumeSessionId) argv.push("--resume", resumeSessionId);
+  // A fork resumes the history into a NEW session id; the original is left as
+  // it was.
+  if (resumeSessionId && forkSession) argv.push("--fork-session");
   if (initialPrompt) argv.push(promptArg(initialPrompt));
   return argv;
 }
@@ -222,6 +226,8 @@ function buildArgv(args, entry) {
  * @param {string} [args.sandbox]
  * @param {string} [args.approval]
  * @param {string} [args.resumeSessionId]
+ * @param {boolean} [args.forkSession] resume `resumeSessionId` into a new
+ *   session id (`claude --fork-session`); Claude only.
  * @param {boolean} [args.resumeLast]
  * @param {boolean} [args.bypass] the user ticked "bypass permissions" for THIS
  *   run; appends the catalog's bypass args/env. Claude has no catalog bypass.
@@ -241,6 +247,7 @@ function spawnRun(args) {
     sandbox,
     approval,
     resumeSessionId,
+    forkSession,
     resumeLast,
     bypass,
     initialPrompt,
@@ -293,6 +300,12 @@ function spawnRun(args) {
   ) {
     throw makeErr("EBADSESSION", "resumeSessionId is not a valid session id");
   }
+  if (forkSession === true) {
+    if (!resumeSessionId) throw makeErr("EBADSESSION", "a fork needs resumeSessionId");
+    if (entry.launcher !== "claude") {
+      throw makeErr("EUNSUPPORTED", `${tool} cannot fork a session`);
+    }
+  }
 
   // A run IS a tmux session, so an absent binary is a precondition failure, not
   // a spawn failure. Without this the caller gets `spawnSync tmux ENOENT` from
@@ -330,6 +343,7 @@ function spawnRun(args) {
       sandbox,
       approval,
       resumeSessionId,
+      forkSession: forkSession === true,
       resumeLast,
       bypass: bypass === true,
       initialPrompt,
@@ -343,7 +357,8 @@ function spawnRun(args) {
     if (!dashboardRuns) return;
     dashboardRuns.recordRun({
       id,
-      sessionId: resumeSessionId || null,
+      // A fork's own id arrives with its first hook (bindRunSession).
+      sessionId: (forkSession !== true && resumeSessionId) || null,
       // `dashboard_runs.mode` is NOT NULL. Passing null made every insert throw
       // inside recordRun's best-effort catch, so no tmux-backed run was ever
       // persisted: publicRun then read its cwd/model/prompt/startedAt off a row