Session tracker and PR attribution hooks were never running

Fixed

• -`tonone-session-tracker.js` and `tonone-pr-attribution.js` never ran: both hooks existed but were not declared in .claude-plugin/plugin.json. Every Skill invocation went untracked and every PR shipped without agent attribution since the hooks were added.
• -`tonone-worktree-session.js` missing: tests expected this SessionStart hook, but it was never created. It now prunes stale git worktrees at session start and emits a ready status so Claude knows whether it's resuming an existing worktree or starting fresh on main.
• -`tonone-worktree-session.js` not registered: implemented but absent from the SessionStart array in plugin.json, making the prune and status features dead code.
• -`tonone-git-gate.js` passed the wrong argument to `EnterWorktree`: the blocked-on-main recovery message passed the branch slug instead of the full worktree path.
• -`tonone-git-gate.js` TOCTOU: two separate execSync calls for --git-dir and --git-common-dir could race if git state changed between calls. Merged into a single atomic invocation.
• -Array bounds bug: git output was split by newline without a length check, so a shorter-than-expected result would incorrectly treat main as a worktree.
• -`tonone-pr-attribution.js` silent failure: a falsy .output field fell through to stringifying the whole object, silently failing to extract the GitHub PR URL on every PR.
• -`bump-version.py` corrupted active worktrees: its glob recursed into .claude/worktrees/, writing version changes into every active worktree. Now excludes it.