feat: Unified create command + consolidated enhancement flags

This commit includes two major improvements:

## 1. Unified Create Command (v3.0.0 feature)
- Auto-detects source type (web, GitHub, local, PDF, config)
- Three-tier argument organization (universal, source-specific, advanced)
- Routes to existing scrapers (100% backward compatible)
- Progressive disclosure: 15 universal flags in default help

**New files:**
- src/skill_seekers/cli/source_detector.py - Auto-detection logic
- src/skill_seekers/cli/arguments/create.py - Argument definitions
- src/skill_seekers/cli/create_command.py - Main orchestrator
- src/skill_seekers/cli/parsers/create_parser.py - Parser integration

**Tests:**
- tests/test_source_detector.py (35 tests)
- tests/test_create_arguments.py (30 tests)
- tests/test_create_integration_basic.py (10 tests)

## 2. Enhanced Flag Consolidation (Phase 1)
- Consolidated 3 flags (--enhance, --enhance-local, --enhance-level) → 1 flag
- --enhance-level 0-3 with auto-detection of API vs LOCAL mode
- Default: --enhance-level 2 (balanced enhancement)

**Modified files:**
- arguments/{common,create,scrape,github,analyze}.py - Added enhance_level
- {doc_scraper,github_scraper,config_extractor,main}.py - Updated logic
- create_command.py - Uses consolidated flag

**Auto-detection:**
- If ANTHROPIC_API_KEY set → API mode
- Else → LOCAL mode (Claude Code)

## 3. PresetManager Bug Fix
- Fixed module naming conflict (presets.py vs presets/ directory)
- Moved presets.py → presets/manager.py
- Updated __init__.py exports

**Test Results:**
- All 160+ tests passing
- Zero regressions
- 100% backward compatible

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/skill_seekers/cli/arguments/__init__.py

@@ -0,0 +1,51 @@
+"""Shared CLI argument definitions.
+
+This module provides a single source of truth for all CLI argument definitions.
+Both standalone modules and unified CLI parsers import from here.
+
+Usage:
+    from skill_seekers.cli.arguments.scrape import add_scrape_arguments
+    from skill_seekers.cli.arguments.github import add_github_arguments
+    from skill_seekers.cli.arguments.pdf import add_pdf_arguments
+    from skill_seekers.cli.arguments.analyze import add_analyze_arguments
+    from skill_seekers.cli.arguments.unified import add_unified_arguments
+    from skill_seekers.cli.arguments.package import add_package_arguments
+    from skill_seekers.cli.arguments.upload import add_upload_arguments
+    from skill_seekers.cli.arguments.enhance import add_enhance_arguments
+
+    parser = argparse.ArgumentParser()
+    add_scrape_arguments(parser)
+"""
+
+from .common import add_common_arguments, COMMON_ARGUMENTS
+from .scrape import add_scrape_arguments, SCRAPE_ARGUMENTS
+from .github import add_github_arguments, GITHUB_ARGUMENTS
+from .pdf import add_pdf_arguments, PDF_ARGUMENTS
+from .analyze import add_analyze_arguments, ANALYZE_ARGUMENTS
+from .unified import add_unified_arguments, UNIFIED_ARGUMENTS
+from .package import add_package_arguments, PACKAGE_ARGUMENTS
+from .upload import add_upload_arguments, UPLOAD_ARGUMENTS
+from .enhance import add_enhance_arguments, ENHANCE_ARGUMENTS
+
+__all__ = [
+    # Functions
+    "add_common_arguments",
+    "add_scrape_arguments",
+    "add_github_arguments",
+    "add_pdf_arguments",
+    "add_analyze_arguments",
+    "add_unified_arguments",
+    "add_package_arguments",
+    "add_upload_arguments",
+    "add_enhance_arguments",
+    # Data
+    "COMMON_ARGUMENTS",
+    "SCRAPE_ARGUMENTS",
+    "GITHUB_ARGUMENTS",
+    "PDF_ARGUMENTS",
+    "ANALYZE_ARGUMENTS",
+    "UNIFIED_ARGUMENTS",
+    "PACKAGE_ARGUMENTS",
+    "UPLOAD_ARGUMENTS",
+    "ENHANCE_ARGUMENTS",
+]