refactor local directory agent to two-phase LLM-with-tools architecture

Replace the single-pass FE-driven agent_run/agent_data flow with a
BE-orchestrated two-phase execution using LangChain tool-calling:
- Phase 1 (Triage): explores directory via new filesystem tools, matches
  files to existing projects using PROJECT_TOOLS
- Phase 2 (Processing): reads files and performs CRUD per project group
  with clean LLM context windows

Key changes:
- Add filesystem_agent.py with list_directory, read_file_content,
  get_file_metadata tools using execute_on_client()
- Move setup journey from REST to WebSocket (journey_start/message frames)
- Add batch_runs_per_day billing limit and enforce in /trigger
- Remove deprecated agent_data/agent_complete frame handlers and queues

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

app/schemas.py

@@ -142,9 +142,6 @@ class WsFrameType(str, Enum):
     tool_result = "tool_result"
     final = "final"
     ping = "ping"
-    agent_run = "agent_run"
-    agent_data = "agent_data"
-    agent_complete = "agent_complete"
     device_hello = "device_hello"
     # ── v3 frame types ─────────────────────────────────────────────────
     home_request = "home_request"
@@ -156,6 +153,10 @@ class WsFrameType(str, Enum):
     data_request = "data_request"
     data_response = "data_response"
     mutation = "mutation"
+    # ── v4 journey frame types ────────────────────────────────────────
+    journey_start = "journey_start"
+    journey_message = "journey_message"
+    journey_reply = "journey_reply"
 
 
 class WsToolCall(BaseModel):
@@ -208,31 +209,6 @@ class WsDeviceHello(BaseModel):
     agent_ids: list[str] = Field(default_factory=list)
 
 
-class WsAgentRun(BaseModel):
-    """Server → Client: trigger an agent run on the connected device."""
-
-    type: Literal[WsFrameType.agent_run] = WsFrameType.agent_run
-    run_id: str
-    agent_id: str
-    config: dict[str, Any]
-
-
-class WsAgentData(BaseModel):
-    """Client → Server: files read by the local agent."""
-
-    type: Literal[WsFrameType.agent_data] = WsFrameType.agent_data
-    run_id: str
-    files: list[dict[str, Any]]
-
-
-class WsAgentComplete(BaseModel):
-    """Client → Server: Electron signals it has finished reading files."""
-
-    type: Literal[WsFrameType.agent_complete] = WsFrameType.agent_complete
-    run_id: str
-    files_read: int
-    errors: list[str] = Field(default_factory=list)
-
 
 # ── WebSocket v3 Frame Models ─────────────────────────────────────────
 
@@ -319,6 +295,7 @@ class AgentCreationCheckResponse(BaseModel):
 
 class AgentTriggerRequest(BaseModel):
     directory: str = Field(min_length=1)
+    device_id: str = Field(default="")
     what_to_extract: list[Literal["task", "note", "timeline", "project"]] = Field(min_length=1)
     actions_by_type: dict[
         Literal["task", "note", "timeline", "project"],
@@ -345,18 +322,3 @@ class AgentRunLogResponse(BaseModel):
 
 # ── Chatbot Journey ───────────────────────────────────────────────────
 
-class JourneyStartRequest(BaseModel):
-    agent_type: Literal["local", "cloud"]
-    agent_id: str | None = None
-
-
-class JourneyMessageRequest(BaseModel):
-    session_id: str
-    message: str
-
-
-class JourneyResponse(BaseModel):
-    session_id: str
-    message: str
-    done: bool
-    prompt_template: str | None = None