fix: silence hook stderr when running outside tmux

[asturwebs]

Summary

• Fixes spurious "hook error" message on every Claude Code session start when running outside tmux
• When TMUX_PANE env var is not set, the hook now exits silently instead of logging a WARNING to stderr
• Claude Code treats any stderr output from hooks as an error, so even a benign warning was displayed to the user

Root Cause

hook.py:193 called logger.warning("TMUX_PANE not set...") which writes to stderr via logging.basicConfig(stream=sys.stderr). Since the hook is designed to run as a SessionStart hook, it fires on every Claude Code session — including those outside tmux where it's not applicable.

Changes

src/ccbot/handlers/hook.py (line 192-194):

• Removed logger.warning() call
• Added comment explaining why silent exit is correct behavior

Test plan

• ruff check passes
• ruff format --check passes
• pyright — 0 errors
• Manual: echo '{"session_id":"...","hook_event_name":"SessionStart","cwd":"/tmp"}' | ccbot hook outside tmux — no stderr output

🤖 Generated with Claude Code

[asturwebs]

Note: the 2 failing checks are pre-existing issues on main, not introduced by this PR.

• check (3.12): ruff format --check fails on bot.py (would reformat 1 file) — this file already needs reformatting on the base branch
• check (3.13): Cancelled as a dependency of the above
• claude-review: Internal error in the Claude Code Action, unrelated to this change

This PR's change to hook.py passes both ruff check and ruff format --check cleanly.