fix: smart enhancement dispatcher — Gemini/API mode + root/Docker detection

Fixes issues #289 and #286 (agent switching and Docker/root failures).

enhance_command.py (new smart dispatcher):
- Routes skill-seekers enhance to API mode (Gemini/OpenAI/Claude API)
  when an API key is available, or LOCAL mode (Claude Code CLI) otherwise
- Decision priority: --target flag > config default_agent > auto-detect
  from env vars (ANTHROPIC_API_KEY → claude, GOOGLE_API_KEY → gemini,
  OPENAI_API_KEY → openai) > LOCAL fallback
- Blocks LOCAL mode when running as root (Docker/VPS) with clear error
  message + API mode instructions
- Supports --dry-run, --target, --api-key as first-class flags

arguments/enhance.py:
- Added --target, --api-key, --dry-run, --interactive-enhancement to
  ENHANCE_ARGUMENTS (shared by unified CLI parser and standalone entry point)

enhance_skill_local.py:
- Error output no longer truncated at 200 chars (shows up to 20 lines)
- Detects root/permission errors in stderr and prints actionable hint

config_manager.py:
- Added default_agent field to DEFAULT_CONFIG ai_enhancement section
- Added get_default_agent() and set_default_agent() methods

main.py:
- enhance command routed to enhance_command (was enhance_skill_local)
- _handle_analyze_command uses smart dispatcher for post-analysis enhancement

pyproject.toml:
- skill-seekers-enhance entry point updated to enhance_command:main

Tests: 1977 passed, 0 failed (28 new tests in test_enhance_command.py)

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

pyproject.toml

@@ -185,7 +185,7 @@ skill-seekers-scrape = "skill_seekers.cli.doc_scraper:main"
 skill-seekers-github = "skill_seekers.cli.github_scraper:main"
 skill-seekers-pdf = "skill_seekers.cli.pdf_scraper:main"
 skill-seekers-unified = "skill_seekers.cli.unified_scraper:main"
-skill-seekers-enhance = "skill_seekers.cli.enhance_skill_local:main"
+skill-seekers-enhance = "skill_seekers.cli.enhance_command:main"
 skill-seekers-enhance-status = "skill_seekers.cli.enhance_status:main"
 skill-seekers-package = "skill_seekers.cli.package_skill:main"
 skill-seekers-upload = "skill_seekers.cli.upload_skill:main"