Fix vmk_data MCP server URL: add /mcp endpoint path ...

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

Add vmk_data MCP server and realtor profile for real estate search ...

- mcp_servers.d/vmk_data.json: streamable_http to localhost:8080

- navi/profiles/realtor/: config + system_prompt + subagent_system_prompt

Profile includes semantic & FTS search, listing details, schema tools

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>