feat: integrate navi_ui MCP server (card_grid + form) into master ...

Port the internal navi_ui MCP server from the vmkdemo branch (it never
landed on master). The server exposes render_component, which returns a
structured JSON envelope; navi/mcp/tools.py extracts metadata.ui_component
onto the role="tool" message, and the webclient renders the component
(card_grid, form) inline inside the assistant turn.

Backend
- navi/mcp/ui_server/: FastMCP server + component registry with card_grid
  and form components (pydantic-validated payloads, LLM-friendly schema docs)
- mcp_servers.d/navi_ui.json: streamable_http config, group "ui"
- config.py: navi_ui_mcp_enabled/host/port flags
- main.py: start UI server in lifespan (task + wait-for-ready + cancel)
- mcp/tools.py: navi_ui envelope parsing; "Error:" results surface as
  failed tool calls so the UI card is not green
- orchestrator.py + agent.py: run_stream(hidden=) for form submissions
  (single is_display=False, is_context=True user message)
- api/websocket.py: extract _start_agent_run helper, add form_submit
  branch that delivers submitted form values as a hidden user message
- profiles/secretary: enable navi_ui "ui" group (agent + subagent)
- .env.example: NAVI_UI_MCP_* flags
- tests/unit/mcp/test_ui_server.py

Webclient
- components/ui/{registry.js,CardGrid.vue,Form.vue}: auto-discovered
  renderers (snake_case <-> PascalCase aliasing)
- components/messages/UiComponentCard.vue: wrapper rendered in
  AssistantMessage when entry.kind === 'ui_component'
- stores/chat.js: extract ui_component from tool_call metadata in both
  live stream and history-replay paths
- composables/useWebSocket.js: note that ui_component rides tool_call
- tests/unit/components/ui/* (17 tests)
- dist rebuilt

Excluded from the vmkdemo port: the stale single-file navi/mcp/ui_server.py
duplicate, the realtor profile, and the vmk_data server (unrelated real
estate work that was interleaved with navi_ui on vmkdemo).

Co-Authored-By: Claude <noreply@anthropic.com>

Add session search across messages with backend + frontend ...

Backend:
- GET /sessions now accepts `search` query param
- _session_summary computes match_indices and match_preview from messages
- pg_session_store: messages ILIKE added to search_list and count_all
- In-memory store: search_list also filters by message content

Frontend:
- AppSidebar: search toggle icon + debounced input, Ctrl+K shortcut
- SessionItem: highlight matching text, show match_preview from search
- SessionList: pass searchQuery to SessionItem
- SessionsStore: searchQuery/searchActive state, setSearch/clearSearch
- API layer: getSessions accepts search param
- MessageList: scroll to target message + brightness flash animation
- ChatStore: loadSession accepts targetMessageIndex, scrollToMessageIndex ref
- CSS: msg-flash keyframe animation in app.scss
- Tests updated for new getSessions signature

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Paginate session list loading

Refine 3D modeler workflow

Add webclient unit tests (Vitest) — 47 tests ...

- Vitest + @vue/test-utils + happy-dom setup
- api/index.test.js: 8 tests for fetch wrapper, verbs, errors, FormData
- stores/chat.test.js: 23 tests for buildMessageList, WS handlers, load/clear
- stores/sessions.test.js: 6 tests for fetch, create, delete, pin, preview
- stores/profiles.test.js: 3 tests for fetch, auto-select, lookup
- composables/useWebSocket.test.js: 7 tests with MockWebSocket
- Export buildMessageList from chat store so tests can verify message parsing
- Update docs/testing.md with webclient stack, layout, and commands

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>