Merge critical PR fixes locally (no push)

- PR #372 (Dave): strip YAML fences from commands/caveman-init.toml — Gemini CLI's FileCommandLoader rejected the file with 'Failed to parse TOML' on extension install. Verified main was broken.
- PR #350 intent (David): rename codex_hooks → hooks in .codex/config.toml. Codex source confirms canonical key is now 'hooks'; codex_hooks is a legacy alias that emits a deprecation log.

Closes #372 #326 (duplicate) #350 locally — push deferred.

.codex/config.toml

@@ -1,2 +1,2 @@
 [features]
-codex_hooks = true
+hooks = true

commands/caveman-init.toml

@@ -1,4 +1,2 @@
----
 description = "Drop the always-on caveman activation rule into the current repo for every IDE agent"
 prompt = "Run `node src/tools/caveman-init.js {{args}}` in the current repo and report the result. Use --dry-run first if the user did not pass --force, so we never silently overwrite an existing rule file."
----