docs: update docs for tools.agent/tools.subagent and Navi Code TUI ...

- profiles.md: document tools.agent/tools.subagent structure, deprecate enabled_tools
- tools.md: move web tools to MCP section, fix mcp__navi-web__* names, add create_mcp_server/test_mcp_tool/mcp_status/recall tools
- api.md: update /agents/profiles and /admin/profiles/{id} response schemas, fix MCP examples
- navi_code.md: correct navi_code tool list (MCP disabled)
- navi_code_cli.md: add /thinking, /compact, correct TUI layout
- index.md: add navi_code, terminal client, pydantic-settings
- testing.md: refresh test directory layout, replace stale coverage roadmap
- agent.md: mention tools.agent/tools.subagent in loop
- archive obsolete eval_system_design.md, plan_navi_code.md, plan_navi_code_tui.md

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