chore(config): centralize git for teammates and enable tmux panes

Two agent-team tooling changes:

- teammateMode: in-process -> auto. Teammates now spawn in tmux split panes
  when the lead runs inside tmux, with graceful in-process fallback.
- New PreToolUse hook git-centralize-guard.sh blocks .git-mutating commands
  (add, commit, merge, push, pull, rebase, reset, checkout, stash,
  cherry-pick, rm, mv) for teammates, keeping version control centralized to
  the lead. Detection keys on the agent_type field, which a teammate's hook
  input carries and the lead's does not. Read-only git is allowed.

Documented in .claude/rules/git-safety.md. Hooks load at lead startup, so a
restart is required for the hook to reach teammates.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.claude/rules/git-safety.md

@@ -7,6 +7,21 @@
 - Skip files in `.gitignore`
 - The `.claude/` directory IS tracked — skills and agents belong in the repo
 
+## Centralized version control (agent teams)
+
+Git is the **team lead's** job. Teammates edit files; the lead stages, commits,
+merges, and pushes. This is enforced, not just convention:
+
+- **Hook:** `.claude/hooks/git-centralize-guard.sh` (PreToolUse on Bash) blocks
+  `.git`-mutating commands — `add`, `commit`, `merge`, `push`, `pull`, `rebase`,
+  `reset`, `checkout`, `stash`, `cherry-pick`, `rm`, `mv` — for any agent-team
+  teammate. Read-only git (`status`, `log`, `diff`, `show`, `fetch`) is allowed.
+- **Detection:** a teammate's PreToolUse hook input carries an `agent_type` field
+  (e.g. `"qatux"`); the lead's main session does not. Present → block; absent →
+  allow. (Confirmed on Claude Code 2.1.148.)
+- **Activation:** hooks load at lead startup and teammates inherit that snapshot,
+  so changes to this hook require a Claude Code restart to reach teammates.
+
 ## Commit conventions
 
 Use conventional commits: `<type>(<scope>): <summary>`