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/unified.py

@@ -0,0 +1,52 @@
+"""Unified command argument definitions.
+
+This module defines ALL arguments for the unified command in ONE place.
+Both unified_scraper.py (standalone) and parsers/unified_parser.py (unified CLI)
+import and use these definitions.
+"""
+
+import argparse
+from typing import Dict, Any
+
+
+UNIFIED_ARGUMENTS: Dict[str, Dict[str, Any]] = {
+    "config": {
+        "flags": ("--config", "-c"),
+        "kwargs": {
+            "type": str,
+            "required": True,
+            "help": "Path to unified config JSON file",
+            "metavar": "FILE",
+        },
+    },
+    "merge_mode": {
+        "flags": ("--merge-mode",),
+        "kwargs": {
+            "type": str,
+            "help": "Merge mode (rule-based, claude-enhanced)",
+            "metavar": "MODE",
+        },
+    },
+    "fresh": {
+        "flags": ("--fresh",),
+        "kwargs": {
+            "action": "store_true",
+            "help": "Clear existing data and start fresh",
+        },
+    },
+    "dry_run": {
+        "flags": ("--dry-run",),
+        "kwargs": {
+            "action": "store_true",
+            "help": "Dry run mode",
+        },
+    },
+}
+
+
+def add_unified_arguments(parser: argparse.ArgumentParser) -> None:
+    """Add all unified command arguments to a parser."""
+    for arg_name, arg_def in UNIFIED_ARGUMENTS.items():
+        flags = arg_def["flags"]
+        kwargs = arg_def["kwargs"]
+        parser.add_argument(*flags, **kwargs)