feat: wire --local-repo-path into create command and add validation

- Add --local-repo-path to UNIVERSAL_ARGUMENTS in create.py so it is
  registered in the actual parser (not just help display)
- Add --local-repo-path to GITHUB_ARGUMENTS in arguments/github.py for
  the standalone github subcommand
- Forward --local-repo-path through create_command._route_github() to
  github_scraper
- Add local_repo_path to the config dict built from CLI args in
  github_scraper.main()
- Add early validation in GitHubScraper.__init__(): warn and reset to
  None if path does not exist, triggering a real GitHub API fallback
  instead of silently operating with an empty file tree (fixes #281)
- Update test_create_arguments.py count/names assertions (17 -> 18)

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

src/skill_seekers/cli/arguments/create.py

@@ -145,6 +145,14 @@ UNIVERSAL_ARGUMENTS: dict[str, dict[str, Any]] = {
             "help": "Preview workflow stages without executing (requires --enhance-workflow)",
         },
     },
+    "local_repo_path": {
+        "flags": ("--local-repo-path",),
+        "kwargs": {
+            "type": str,
+            "help": "Path to local clone of a GitHub repository for unlimited C3.x analysis (bypasses GitHub API file limits)",
+            "metavar": "PATH",
+        },
+    },
 }
 
 # Merge RAG arguments from common.py into universal arguments