fix(codex): block unsupported execute worktrees

bin/install.js

@@ -2334,6 +2334,10 @@ Direct mapping:
   at install time so \`model_overrides\` from \`.planning/config.json\` and
   \`~/.gsd/defaults.json\` are honored automatically by Codex's agent router.
 - \`fork_context: false\` by default — GSD agents load their own context via \`<files_to_read>\` blocks
+- \`Task(isolation="worktree")\` / \`Agent(isolation="worktree")\` → no direct Codex mapping.
+  Codex \`spawn_agent\` does not create or bind a git worktree automatically.
+  Workflows that require this isolation must fail closed or use an explicit
+  manual worktree protocol before spawning (#3360).
 
 Spawn restriction:
 - Codex restricts \`spawn_agent\` to cases where the user has explicitly