webclient: MCP user keys panel (BYOK) + frontend tests

webclient: W4 — chat empty state -> GnEmptyState, card modal -> GnModal ...

- ChatArea: .empty-chat custom icon+text -> GnEmptyState card
  (keep .empty-chat wrapper only for centering)
- CardGrid: inline Teleport modal (overlay/close/scroll bespoke chrome
  removed) -> GnModal; .card-modal/.card-modal-title class names kept
  inside the new DOM (test contract); kit header slot renders the title
- WelcomeScreen: typography aligned to kit (30px h1, 14px base),
  profile cards get -radius-md, dead .profile-icon style dropped
- CardGrid test: mount with the kit plugin (GnModal resolves),
  two nextTicks for the post-flush open watcher

Verified: vitest 111 passed, build OK, welcome screenshot unchanged
(modal/empty-state visually checked after final build)

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>