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/settings.json

@@ -4,7 +4,7 @@
     "CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS": "1",
     "SR_DB_PATH": "/var/home/jeroenschweitzer/Projects/settled-reach/settledreach.db"
   },
-  "teammateMode": "in-process",
+  "teammateMode": "auto",
   "permissions": {
     "allow": [
       "Bash(git add *)",
@@ -87,6 +87,11 @@
             "type": "command",
             "command": ".claude/hooks/git-lock-guard.sh",
             "timeout": 5
+          },
+          {
+            "type": "command",
+            "command": ".claude/hooks/git-centralize-guard.sh",
+            "timeout": 5
           }
         ]
       }