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>

Update gnexus-creds MCP instructions: require tags, category, and allow_mcp ...

- Add rule to always include `tags` and `category` when creating secrets
- Add rule to always set `allow_mcp=true` so secrets remain visible through MCP

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

Add MCP streamable_http transport, integrate gnexus-creds, and document headless nodes ...

- navi/mcp/client.py: add streamable_http transport via httpx + mcp.client.streamable_http
- navi/mcp/config.py: add "streamable_http" to transport literal and is_streamable_http property
- mcp_servers.d/gnexus-creds.json: new MCP server config with overlay instructions for secret workflow
- docs/future_headless_nodes.md: architecture exploration for headless Navi node swarm

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

Migrate MCP tool naming from mcp:server:tool to mcp__server__tool ...

The colon separator (mcp:server:tool) confuses many LLMs during
tool-calling because colons appear in schemas and URLs. Switch to
double-underscore separator (mcp__server__tool) for robust parsing.

Key changes:
- navi/mcp/tools.py: add build_mcp_name(), parse_mcp_name(), is_mcp_tool()
- navi/core/tool_executor.py: update _resolve_tool() with new helpers
  and legacy colon fallback for old sessions
- navi/core/tool_utils.py, subagent_runner.py: use build_mcp_name()
- navi/api/routes/{admin,agents}.py: prefix via build_mcp_name()
- navi/tools/{list_tools,reload_tools}.py: migrated
- All profile configs + system_prompt.txt: replace mcp: with mcp__
- manuals/{model_3d,lint_scad,render_3d,spawn_agent}.md: updated
- mcp_servers.d/gnexus-book.json: instructions updated
- docs/{api,profiles,tools,mechanics,visual.html}: updated
- tests: test_tool_executor.py and test_mcp.py aligned

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

chore: remove test MCP servers from repo ...

project_health and time_toolkit were created for development testing
and should not be part of the committed codebase.

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

refactor: migrate MCP config to directory-based mcp_servers.d ...

Replaces monolithic mcp_servers.json with per-server files in
mcp_servers.d/<name>.json. Filename stem becomes the server name.

- load_mcp_servers() reads directory globs, auto-migrates legacy file
- save_mcp_servers() writes per-server files, cleans up stale ones
- Update docstrings in manager.py and context_builder.py

Auto-migration: existing servers (gnexus-book, navi-3d, navi-web) plus
new ones (project_health, time_toolkit) now live in mcp_servers.d/.

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