agents: scope git hygiene hook to git add commands

The `PreToolUse:Bash` hook invoked `enforce-git-hygiene.sh` on every Bash tool call, even though the script only blocks `git add . / -A / --all`. Add `"if": "Bash(git add *)"` so the script only runs when the command actually contains `git add`.

.agents/settings.json

@@ -16,6 +16,7 @@
         "hooks": [
           {
             "type": "command",
+            "if": "Bash(git add *)",
             "command": "bash .agents/hooks/enforce-git-hygiene.sh"
           }
         ],