Add Windows support for IPC with TCP and port file discovery

[abnegate]

Summary

This PR extends the IPC (Inter-Process Communication) system to support Windows by replacing Unix domain sockets with TCP connections on localhost, while maintaining Unix socket support on Unix-like systems.

Key Changes

IPC Module (src/ipc/mod.rs)

• Updated module documentation to reflect cross-platform IPC support
• Modified ipc_runtime_dir() to use platform-specific directories:
  • Windows: %LOCALAPPDATA%\claudear with fallback to %TEMP%\claudear
  • Unix: XDG_RUNTIME_DIR (Linux) or claudear-{uid} in temp directory with 0700 permissions
• Changed default_socket_path() to return .port files on Windows and .sock files on Unix
• Updated is_daemon_running() to check TCP connectivity on Windows (reading port from file) and Unix socket connectivity on Unix
• Added read_port_from_file() and write_port_file() helper functions for Windows port file management
• Enhanced cleanup_stale_files() to handle both socket and port file cleanup across platforms
• Added Windows process checking via OpenProcess API with PROCESS_QUERY_LIMITED_INFORMATION
• Updated tests to use platform-appropriate file extensions and paths

IPC Client (src/ipc/client.rs)

• Updated documentation to reflect TCP support on Windows
• Modified send_internal() to support both Unix sockets and TCP connections:
  • Unix: connects directly to Unix domain socket
  • Windows: reads port from port file, then connects via TCP to 127.0.0.1:{port}
• Updated is_daemon_running() with platform-specific logic
• Fixed test paths to use std::env::temp_dir() instead of hardcoded /tmp paths

IPC Server (src/ipc/server.rs)

• Updated documentation to reflect TCP support on Windows
• Modified run() to bind to appropriate listener:
  • Unix: UnixListener on socket path
  • Windows: TcpListener on 127.0.0.1:0 (OS-assigned port), writes port to port file
• Added separate handle_connection() implementations for Unix (UnixStream) and Windows (TcpStream)
• Both implementations maintain identical command handling logic

Tool Detection (src/evaluation/detector.rs)

• Updated which_exists() to use where command on Windows instead of which
• Updated test to check for cmd on Windows and ls on Unix

Dependencies (Cargo.toml)

• Added windows-sys dependency with Win32_Foundation and Win32_System_Threading features for Windows process checking
• Ensured tokio includes net feature for TCP support

Storage (src/storage/vectorlite.rs)

• Added Windows DLL path (./vectorlite.dll) to vectorlite library search paths

Implementation Details

• Port Discovery: On Windows, the server writes the assigned TCP port to a port file, which the client reads to establish connections
• Security: Windows uses %LOCALAPPDATA% which is user-private by default; Unix maintains strict 0700 permissions on runtime directories
• Backward Compatibility: Unix systems continue using Unix domain sockets; no changes to existing Unix behavior
• Process Checking: Windows uses OpenProcess with read-only flags; Unix uses /proc or kill -0 as before

https://claude.ai/code/session_01Mmu98Tc4ZbqpRzMCsVCkXd