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/create_command.py

@@ -209,6 +209,8 @@ class CreateCommand:
             argv.extend(["--max-issues", str(self.args.max_issues)])
         if getattr(self.args, "scrape_only", False):
             argv.append("--scrape-only")
+        if getattr(self.args, "local_repo_path", None):
+            argv.extend(["--local-repo-path", self.args.local_repo_path])
 
         # Call github_scraper with modified argv
         logger.debug(f"Calling github_scraper with argv: {argv}")