feat(llm): add llm-catalog and llm-check commands, rename helper → llm-helper

Consistent llm-* naming scheme for all LLM CLI commands. llm-catalog shows
provider metadata and key status; llm-check sends a minimal prompt to verify
connectivity.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

markitect/cli.py

@@ -7095,10 +7095,12 @@ try:
 except ImportError:
     pass  # Prompts module not available
 
-# Register helper Q&A command
+# Register LLM commands (llm-helper, llm-catalog, llm-check)
 try:
-    from markitect.helper.cli import helper_command
+    from markitect.helper.cli import helper_command, llm_catalog, llm_check
     cli.add_command(helper_command)
+    cli.add_command(llm_catalog)
+    cli.add_command(llm_check)
 except ImportError:
     pass  # Helper module not available