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).

docs/I18N.md

@@ -132,9 +132,7 @@ classDiagram
       +t(key, params)
     }
 
-    class SidebarLanguageSwitch {
-      +SUPPORTED_LANGUAGES
-      +normalizeLanguage()
+    class SettingsLanguagePicker {
       +changeLanguage()
     }
 
@@ -149,7 +147,7 @@ classDiagram
     I18nConfig --> NamespaceResource
     ReactComponent --> I18nConfig
     ReactComponent --> NamespaceResource
-    SidebarLanguageSwitch --> I18nConfig
+    SettingsLanguagePicker --> I18nConfig
     FormatUtils --> I18nConfig
 ```
 
@@ -157,7 +155,7 @@ classDiagram
 
 ## 4) Language Detection and Switching Flow
 
-The sidebar language controls call `i18n.changeLanguage()` and UI updates reactively through `useTranslation`.
+The language picker in Settings → General (`client/src/pages/Settings.tsx`, a `SettingsSegmented` of English / Tiếng Việt, found by the settings search too) calls `i18n.changeLanguage()` and UI updates reactively through `useTranslation`. The sidebar has no language control.
 
 ```mermaid
 sequenceDiagram
@@ -239,7 +237,7 @@ npm run test:client
 | Locale fallback | Unknown locales fall back to `en` | `vi-VN` resolves to `vi` |
 | Terminology consistency | Canonical terms stay stable | `Agent`/`Subagent` expectations |
 | Date/number formatting | Locale-specific output shape | `en-US`, `vi-VN` formatting |
-| Runtime switching | UI rerenders without reload | Sidebar language toggle |
+| Runtime switching | UI rerenders without reload | Settings → General language picker |
 
 ---
 
@@ -284,7 +282,7 @@ gantt
 ### Operational checklist
 - [ ] Confirm all namespaces exist for `en` and `vi`
 - [ ] Confirm key parity across all locale JSON files
-- [ ] Confirm language switching works in collapsed and expanded sidebar modes
+- [ ] Confirm language switching from Settings → General re-renders the whole app
 - [ ] Confirm fallback behavior for region tags (e.g., `vi-VN`, `en-US`)
 - [ ] Confirm date/time/currency formatting for all supported languages
 - [ ] Confirm client tests pass before release