Fix gnexus-book MCP instructions and add old-format fallback in tool executor ...

- Updated mcp_servers.json gnexus-book instructions to use mcp:gnexus-book:
  prefix instead of the old mcp_gnexus-book_ format.
- Added fallback in tool_executor.py for old underscore format
  (mcp_server_tool → mcp:server:tool) so transitional models still work.
- Added unit test for the old-format fallback.

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

Rename MCP tools to mcp:server:tool format and restore human-readable names ...

- Core naming: mcp_server_tool → mcp:server:tool (colon-delimited)
- navi-web tools: search/view/request → web_search/web_view/http_request
- navi-3d tools: compile_scad/render_stl/lint_scad (unchanged names)
- Updated all profile configs, system prompts, docs, manuals, tests
- Added new lint_scad.md manual
- Fixed modeler_3d prompt stale references (scad_lint, model_3d, render_3d)
- All 240 tests pass

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

Handle MCP tool aliases robustly