Throttle auto-update and remove duplicate fetch logic

[kbrock]

Thank you for the great project

Summary

• Add 3-hour throttle to auto_update() — matches the GitHub Actions update cadence
• Replace duplicated inline fetch/pull in read_doc() with auto_update() call
• /docs -t bypasses the throttle for explicit freshness checks
• Installer removes the no-op PreToolUse hook instead of reinstalling it
• hook-check case arm kept for backward compatibility

Reasoning

• Decided to keep this check on /docs so we would only run if you are actively using the docs command.
• If you don't use the docs command, it will not hit the server every 3 hours.
• Since the docs repo job is every 3 hours, and we check every 3 hours, theoretically, the delay could be up to 6 hours. But there is always /docs -t when you update claude.exe
• This only loads docs 1 time across all Claude shells.
• I had trouble testing since it wanted to blow my code away from your repo.
• Would be nice to only update the docs after Claude is updated, or on a restart.

Test plan

• Run /docs hooks — should read instantly, fetch at most once per 3 hours
• Run /docs -t — should always fetch
• Run installer — should remove existing hook, not add a new one