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/by-file.md

@@ -0,0 +1,83 @@
+# Search by File Path
+
+Find all work related to a specific file.
+
+## When to Use
+
+- User asks: "What changes did we make to auth/login.ts?"
+- Understanding the history of a specific file
+- Finding all observations that touched a file
+
+## Command
+
+```bash
+curl -s "http://localhost:37777/api/search/by-file?filePath=auth/login.ts&limit=10&format=index"
+```
+
+## Parameters
+
+- **filePath** (required): Full or partial file path
+  - Examples: "auth/", "login.ts", "src/components/Button.tsx"
+- **format**: "index" or "full" (default: "full")
+- **limit**: Number of results per type (default: 10, max: 100)
+- **project**: Filter by project name (optional)
+
+## Response Structure
+
+Returns both observations and sessions that touched the file:
+
+```json
+{
+  "filePath": "auth/login.ts",
+  "count": 5,
+  "format": "index",
+  "results": {
+    "observations": [...],
+    "sessions": [...]
+  }
+}
+```
+
+## Use Cases
+
+**Full file path:**
+```bash
+curl -s "http://localhost:37777/api/search/by-file?filePath=src/auth/login.ts&limit=10"
+```
+
+**Partial path (matches all files in directory):**
+```bash
+curl -s "http://localhost:37777/api/search/by-file?filePath=auth/&limit=10"
+```
+
+**Filename only (matches across directories):**
+```bash
+curl -s "http://localhost:37777/api/search/by-file?filePath=login.ts&limit=10"
+```
+
+## How to Present Results
+
+```markdown
+Found 5 changes to auth/login.ts:
+
+**Observations:**
+1. 🟣 **#1234** Implemented JWT authentication
+   > Added token-based auth with refresh tokens
+   > Nov 9, 2024
+
+2. 🔴 **#1235** Fixed token expiration edge case
+   > Handled race condition in refresh flow
+   > Nov 9, 2024
+
+**Sessions:**
+1. **Session #123** (Nov 8, 2024)
+   > Add user authentication
+   > Completed: Implemented JWT auth, added middleware
+```
+
+## Tips
+
+1. Partial paths are powerful for finding all work in a directory
+2. Use this before modifying a file to understand its history
+3. Helps identify who/when/why changes were made
+4. Combine observations + sessions for complete file history