feat: Add search skill with progressive disclosure and refactor existing skills

Enhancements:
- Added search skill with 10 HTTP API endpoints for memory queries
- Refactored version-bump and troubleshoot skills using progressive disclosure pattern
- Added operations/ subdirectories for detailed skill documentation
- Updated CLAUDE.md with skill-based search architecture
- Enhanced worker service with search API endpoints
- Updated CHANGELOG.md with v5.4.0 migration details

Technical changes:
- New plugin/skills/search/ directory with SKILL.md
- New .claude/skills/version-bump/operations/ (workflow.md, scenarios.md)
- New plugin/skills/troubleshoot/operations/ (common-issues.md, worker.md)
- Modified src/services/worker-service.ts (added search endpoints)
- Modified plugin/scripts/worker-service.cjs (rebuilt with search API)
- Reduced main skill files by 89% using progressive disclosure
- Token savings: ~2,250 tokens per session start

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

plugin/skills/search/operations/help.md

@@ -0,0 +1,103 @@
+# API Help
+
+Get comprehensive API documentation from the search service.
+
+## Command
+
+```bash
+curl -s "http://localhost:37777/api/search/help"
+```
+
+## Response
+
+Returns complete API documentation in JSON format including:
+- All 10 endpoint paths
+- HTTP methods (all GET)
+- Parameter descriptions
+- Example curl commands
+
+## Example Response
+
+```json
+{
+  "title": "Claude-Mem Search API",
+  "description": "HTTP API for searching persistent memory",
+  "endpoints": [
+    {
+      "path": "/api/search/observations",
+      "method": "GET",
+      "description": "Search observations using full-text search",
+      "parameters": {
+        "query": "Search query (required)",
+        "format": "Response format: 'index' or 'full' (default: 'full')",
+        "limit": "Number of results (default: 20)",
+        "project": "Filter by project name (optional)"
+      }
+    },
+    // ... 9 more endpoints
+  ],
+  "examples": [
+    "curl \"http://localhost:37777/api/search/observations?query=authentication&format=index&limit=5\"",
+    "curl \"http://localhost:37777/api/search/by-type?type=bugfix&limit=10\"",
+    // ... more examples
+  ]
+}
+```
+
+## When to Use
+
+- User asks: "How do I use the search API?"
+- Need to see all available endpoints
+- Reference for parameter names and formats
+- Getting started with search
+
+## How to Present
+
+```markdown
+## Claude-Mem Search API Documentation
+
+**Base URL:** http://localhost:37777
+**Port:** Configurable via `CLAUDE_MEM_WORKER_PORT` (default: 37777)
+
+### Available Endpoints
+
+**Full-Text Search:**
+1. `GET /api/search/observations` - Search observations by keyword
+2. `GET /api/search/sessions` - Search session summaries
+3. `GET /api/search/prompts` - Search user prompts
+
+**Filtered Search:**
+4. `GET /api/search/by-type` - Filter by observation type
+5. `GET /api/search/by-concept` - Filter by concept tags
+6. `GET /api/search/by-file` - Find work by file path
+
+**Context Retrieval:**
+7. `GET /api/context/recent` - Get recent sessions
+8. `GET /api/context/timeline` - Timeline around a point
+9. `GET /api/timeline/by-query` - Search + timeline in one call
+
+**Documentation:**
+10. `GET /api/search/help` - This help documentation
+
+### Example Usage
+
+\`\`\`bash
+# Search for authentication-related observations
+curl "http://localhost:37777/api/search/observations?query=authentication&format=index&limit=5"
+
+# Get recent bugfixes
+curl "http://localhost:37777/api/search/by-type?type=bugfix&limit=10"
+
+# Get timeline around observation #1234
+curl "http://localhost:37777/api/context/timeline?anchor=1234&depth_before=5&depth_after=5"
+\`\`\`
+
+For detailed information on each endpoint, see the operation-specific documentation files.
+```
+
+## Tips
+
+- This endpoint is useful for quick API reference
+- Most users won't need to use this directly
+- The router SKILL.md provides better user-facing guidance
+- Use this when users specifically ask "how do I use the API"