feat: appbar pickers, multi-agent personas, threads, library, profile

Adds a substantial chrome layer atop the bare template:

Appbar
- Font-size picker (root font-size scale): S/M/L/XL
- Surface picker: tints --background/--card/--popover/--sidebar/--muted/
  --secondary/--accent across light + dark
- Background picker: 11 atmospheric gradients (Pearl, Linen, Mist, Dawn,
  Seafoam, Aurora, Sunset, Meadow, Midnight, Blush, Noir) + None
- Vivid foreground tokens for stronger text contrast; fixed dark-mode
  blue-on-blue user bubble (deeper --primary, near-white --primary-fg)

Assistant route
- Multi-agent personas (~/lib/agents.ts): Atlas, Forge, Inkwell, Pilot,
  Cursor — each with name/role/sub-prompt; per-thread persona; agent
  picker with avatar tint + handoff submenu
- Conversation threads (~/lib/threads.ts): new/switch/rename/delete,
  auto-titling from first user message, per-thread pinned indices
- Compact summarization with snapshot-based Restore that preserves
  pinned messages verbatim
- Edit & retry the last user message, Regenerate, Continue, Show
  system prompt, Copy / Export Markdown, Save to Library, Compare
  across agents (parallel completions in a side-by-side modal)
- Per-message Pin / Read aloud (Web Speech) / Edit
- Voice input via Web Speech Recognition
- Two-column Actions popover (UI Control + Conversation / Share /
  Multi-agent / Clear sections)
- Status bar: connection dot + LOCAL/API/MOCK chip + host chip +
  context progress bar
- Compactly named threads picker; New conversation
- DropdownMenuItem onSelect → onClick (base-ui Menu fires onClick)

Library
- ~/lib/library.ts store, /library route with search + detail panel
  (Copy / Download / Delete)

Profile
- /profile route + ~/lib/profile.ts (name/email/title/bio/signature/
  avatar dataURL/default agent), AppShell uses live profile for the
  appbar avatar; account menu now navigates to /profile

Settings
- Sub-sidenav (LLM / Agents / Appearance / Account / About)
- Editable system prompt with reset-to-default
- Agents CRUD panel
- Reorganized layout

UI Control
- Static action catalog in the system prompt so the assistant can
  drive controls on routes that aren't currently mounted
- Always returns to /assistant after a UI Control sequence (model-
  side rule + deterministic safety net)
- Cursor uses click-nav over direct navigate so the virtual cursor
  is visibly involved
- New ids tagged across the app (sidebar, settings, profile, library,
  assistant tools, agent handoff, thread management)

Hydration
- root.tsx: suppressHydrationWarning on html/body since the pre-mount
  script sets dark/data-bg/data-surface/data-font-scale before React

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

app/components/assistant/message-body.tsx

@@ -56,7 +56,7 @@ export function MessageBody({ content }: { content: string }) {
       )}
       {actionCount > 0 && (
         <span
-          className="mt-1 inline-flex items-center gap-1.5 rounded-full border border-primary/30 bg-primary/10 px-2.5 py-0.5 text-xs font-medium text-primary"
+          className="mt-1 inline-flex items-center gap-1.5 rounded-full border border-primary/40 bg-primary/10 px-2.5 py-0.5 text-xs font-medium text-primary dark:border-sky-400/60 dark:bg-sky-400/15 dark:text-sky-200"
           title="Action block executed by the command bus"
         >
           <Sparkles className="size-3" />