Frontend tool-panel registry + feature slices

[LukeMainwaring]

Summary

Replaces the hardcoded per-tool branching in components/message.tsx with a registry lookup, and moves the domain panel components into features/<name>/ slices. Adding a tool panel is now: create the component in its slice + add one map entry — message.tsx never changes again for new tools.

Registry contract

• features/tool-panel-registry.ts is the composition root — the only file that imports across feature slices. It spreads each slice's Record<string, ToolPanelEntry> map into TOOL_PANELS.
• A ToolPanelEntry is { Panel: ComponentType<{ input: unknown; output: unknown }>, hideRawOutput?: boolean }. Wrapper components in each slice own the input/output parsing that previously lived in message.tsx.
• message.tsx does a single TOOL_PANELS[toolName] lookup and renders the panel when part.state === "output-available".

Slice layout

features/
  tool-panel-registry.ts
  sessions/
    session-visualization.tsx   (moved; emotion-trajectory import now relative)
    emotion-trajectory.tsx      (moved, unchanged)
    session-list-panel.tsx      (moved; chat-actions-provider import now aliased)
    tool-panels.tsx             (new: analyze_session, list_sessions)
  retrieval/
    retrieved-tracks-panel.tsx  (moved; waveform-viz import now relative)
    waveform-viz.tsx            (moved, unchanged)
    tool-panels.tsx             (new: retrieve_tracks_from_brain_state)
lib/
  extract-session-id.ts         (new: shared input parser — both slices need it)

The list_sessions HTML-comment ID extraction (and its rationale comment) moved into the sessions slice, since it's specific to that tool. brain-context-badge.tsx stays in components/ — it's chat chrome, not a tool panel.

Behavior preservation

• Panels mount only on output-available.
• Unregistered tools fall back to the raw <ToolCall> JSON view.
• Only list_sessions hides the raw output block (hideRawOutput: true).
• A failed session_id parse renders no panel (wrapper returns null), exactly as before.

Verification

• pnpm -C frontend format + pnpm -C frontend lint — clean.
• pnpm -C frontend exec tsc --noEmit — clean.
• git diff --stat main -- frontend/api/generated — empty (no backend/API changes, no client regen).

🤖 Generated with Claude Code