Rewrite run_local_agent: code-based flow, concurrency guard, remove isApproved

- Replace LLM-driven triage with code-based directory scan and project fetch
- Two-step LLM approach: Step 1 classifies file→project+domains, Step 2 processes with tools
- Add domain descriptions to Step 1 prompt for better extraction accuracy
- Add _running_agents set for per-agent concurrency guard (one running instance per agent)
- Return 409 from route before DB write when agent already running
- Remove is_approved from task_agent create/update tools and system prompt
- Remove is_approved from timeline_agent create/update tools and system prompt

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/api/routes/agents.py

@@ -21,7 +21,7 @@ from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.api.deps import get_current_user
 from app.billing.tier_manager import FEATURES
-from app.core.agent_runner import run_local_agent
+from app.core.agent_runner import is_agent_running, run_local_agent
 from app.core.device_manager import device_manager
 from app.db import get_session
 from app.models import AgentRunLog, LocalAgentConfig
@@ -193,6 +193,12 @@ async def trigger_agent_run(
     # Use the FE's stable agent_id if provided, fall back to the ephemeral config id.
     stable_agent_id = body.agent_id or config.id
 
+    if is_agent_running(stable_agent_id):
+        raise HTTPException(
+            status_code=status.HTTP_409_CONFLICT,
+            detail="Agent is already running. Only one run per agent is allowed at a time.",
+        )
+
     run_log = AgentRunLog(
         agent_id=stable_agent_id,
         agent_type="local",