ci: update docs validation paths and cleanup test files

- Rename docs/11_agents to docs/agents in workflow paths
- Add DATA_DIR environment variable support to agent-registry (defaults to /var/lib/aitbc)
- Remove obsolete test files (test_host_miner.py, test_transactions_display.py)

apps/agent-services/agent-registry/src/app.py

@@ -10,11 +10,16 @@ from typing import List, Optional, Dict, Any
 import json
 import time
 import uuid
+import os
 from datetime import datetime, UTC, timedelta
 import sqlite3
 from contextlib import contextmanager
 from contextlib import asynccontextmanager
 
+# Database path - use DATA_DIR environment variable or fallback to /var/lib/aitbc
+DATA_DIR = os.environ.get('DATA_DIR', '/var/lib/aitbc')
+DB_PATH = os.path.join(DATA_DIR, 'agent_registry.db')
+
 @asynccontextmanager
 async def lifespan(app: FastAPI):
     # Startup
@@ -27,7 +32,7 @@ app = FastAPI(title="AITBC Agent Registry API", version="1.0.0", lifespan=lifesp
 
 # Database setup
 def get_db():
-    conn = sqlite3.connect('agent_registry.db')
+    conn = sqlite3.connect(DB_PATH)
     conn.row_factory = sqlite3.Row
     return conn