Extension hooks (after_tasks, after_implement) are never triggered #1701

I built an extension with an after_tasks hook. It installs fine, registers in .specify/extensions.yml, but never fires after /speckit.tasks.

Looking at the source, HookExecutor in extensions.py is fully implemented — registering, condition evaluation, formatting all work. But check_hooks_for_event() is never called by anything. The core templates (templates/commands/tasks.md, implement.md) have no references to hooks or extensions.yml. The tasks.md has handoffs but no hook checking.

The RFC has a "Hook Execution" section showing exactly what to add to core templates — parsing extensions.yml and outputting EXECUTE_COMMAND: markers. This was never added.

To reproduce:

1. Create extension with after_tasks hook, install it
2. Confirm hooks registered in .specify/extensions.yml
3. Run /speckit.tasks to completion
4. No hook prompt, no output — hook silently ignored

Versions: CLI 0.1.6, template v0.1.6, Python 3.11.9, macOS arm64

Looks like #1551 shipped the backend but the template wiring from the RFC wasn't included. Is this planned?