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/agents/__init__.py

@@ -1,5 +1,5 @@
 """Expose tool modules used by deep orchestrator-worker graphs."""
 
-from app.agents import timeline_agent, note_agent, project_agent, task_agent
+from app.agents import filesystem_agent, timeline_agent, note_agent, project_agent, task_agent
 
-__all__ = ["timeline_agent", "note_agent", "project_agent", "task_agent"]
+__all__ = ["filesystem_agent", "timeline_agent", "note_agent", "project_agent", "task_agent"]

app/agents/filesystem_agent.py

@@ -0,0 +1,85 @@
+"""Filesystem agent — tools for reading local directories and files on Electron.
+
+These tools delegate to the Electron client via ``execute_on_client()`` using
+the same WS tool-call round-trip pattern as CRUD tools.  The Electron app
+handles actual disk I/O and responds with ``tool_result`` frames.
+"""
+
+from __future__ import annotations
+
+from typing import Any
+
+from langchain_core.tools import tool
+
+from app.core.ws_context import execute_on_client
+
+
+@tool
+async def list_directory(path: str) -> str:
+    """List files and folders in a local directory on the user's device.
+
+    Returns a formatted listing of entries with name, type (file/directory),
+    and full path.
+    """
+    result = await execute_on_client(
+        action="list_directory",
+        data={"path": path},
+    )
+    entries: list[dict[str, Any]] = result.get("entries", [])
+    if not entries:
+        return f"Directory '{path}' is empty or does not exist."
+    lines: list[str] = []
+    for entry in entries:
+        entry_type = entry.get("type", "unknown")
+        entry_name = entry.get("name", "")
+        entry_path = entry.get("path", "")
+        lines.append(f"- [{entry_type}] {entry_name}  ({entry_path})")
+    return f"Directory listing for '{path}' ({len(entries)} entries):\n" + "\n".join(lines)
+
+
+@tool
+async def read_file_content(path: str) -> str:
+    """Read the text content of a local file on the user's device.
+
+    Returns the file content as a string.  Large files may be truncated
+    by the Electron client.
+    """
+    result = await execute_on_client(
+        action="read_file_content",
+        data={"path": path},
+    )
+    content: str = result.get("content", "")
+    if not content:
+        return f"File '{path}' is empty or could not be read."
+    return content
+
+
+@tool
+async def get_file_metadata(path: str) -> str:
+    """Get metadata for a local file: size, creation date, modification date, extension.
+
+    Returns a formatted summary of the file's metadata.
+    """
+    result = await execute_on_client(
+        action="get_file_metadata",
+        data={"path": path},
+    )
+    size = result.get("size", "unknown")
+    created = result.get("createdAt", "unknown")
+    modified = result.get("modifiedAt", "unknown")
+    extension = result.get("extension", "unknown")
+    name = result.get("name", path)
+    return (
+        f"File: {name}\n"
+        f"  Extension: {extension}\n"
+        f"  Size: {size} bytes\n"
+        f"  Created: {created}\n"
+        f"  Modified: {modified}"
+    )
+
+
+FILESYSTEM_TOOLS: list[Any] = [
+    list_directory,
+    read_file_content,
+    get_file_metadata,
+]