docs: index, profiles, tools, api actualization + archive historical docs ...

index.md: expand the file map to reference navi_code, navi_code_cli, store,
context_providers, eval_system, android-client, testing; point at archive/
for historical notes.

profiles.md: add the Compression section (compression_keep_recent /
compression_max_tokens / compression_prompt_file overrides), the
subagent_system_prompt field, and a note that AgentProfile allows unknown
keys (model_config extra=allow).

tools.md: rewrite the user-tools self-extension section — write_tool is
deprecated and removed; write the file via filesystem/code_exec and call
reload_tools instead.

api.md: add missing REST endpoints (GET /sessions/{id}/todos, GET
/sessions/{id}/files list, GET /sessions/{id}/messages/archive, POST
/sessions/{id}/stop) and the admin MCP management block (config CRUD,
reconnect, status, test, profile-mcp mapping, admin recalls); fix the
WS client→server table (type: message|compact, image limits 8/50MB);
add model_info / todo_updated / compression_started events; fix
recall_update action (add skipped), session_sync payload, context_compressed
threshold (70%).

Archive: move plan_01_god_object_agent.md, tech_debt_review_2026-04-29.md,
architecture_weak_spots.md, future_headless_nodes.md into docs/archive/
(historical design notes, no inbound links).

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