[Feature Request] Agents need built-in access to current Claude Code documentation

Claude Code agents currently can't answer questions about CLI commands, features, or settings without redirecting users to /help or
external docs. This breaks agent autonomy and creates friction.

Request: Implement semantic search + retrieval of relevant documentation sections (not full docs), combined with prompt caching for
efficiency. Bundle documentation in the harness and version it with releases so agents always have current information.

Impact: Agents become truly autonomous. Users get instant answers about features without manual lookups. Token overhead is minimal (~200-300 tokens per on-demand query, cached on follow-ups).

Example: Instead of "run /help to find that", agents could answer "Haiku 4.5 supports low, medium, and high effort levels. xhigh is Opus 4.7 only."