feat: add interactive terminal and dev server management

Add new features for interactive terminal sessions and dev server control:

Terminal Component:
- New Terminal.tsx component using xterm.js for full terminal emulation
- WebSocket-based PTY communication with bidirectional I/O
- Cross-platform support (Windows via winpty, Unix via built-in pty)
- Auto-reconnection with exponential backoff
- Fix duplicate WebSocket connection bug by checking CONNECTING state
- Add manual close flag to prevent auto-reconnect race conditions
- Add project tracking to avoid duplicate connects on initial activation

Dev Server Management:
- New DevServerControl.tsx for starting/stopping dev servers
- DevServerManager service for subprocess management
- WebSocket streaming of dev server output
- Project configuration service for reading package.json scripts

Backend Infrastructure:
- Terminal router with WebSocket endpoint for PTY I/O
- DevServer router for server lifecycle management
- Terminal session manager with callback-based output streaming
- Enhanced WebSocket schemas for terminal and dev server messages

UI Integration:
- New Terminal and Dev Server tabs in the main application
- Updated DebugLogViewer with improved UI and functionality
- Extended useWebSocket hook for terminal message handling

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

server/routers/devserver.py

@@ -0,0 +1,280 @@
+"""
+Dev Server Router
+=================
+
+API endpoints for dev server control (start/stop) and configuration.
+Uses project registry for path lookups and project_config for command detection.
+"""
+
+import re
+import sys
+from pathlib import Path
+
+from fastapi import APIRouter, HTTPException
+
+from ..schemas import (
+    DevServerActionResponse,
+    DevServerConfigResponse,
+    DevServerConfigUpdate,
+    DevServerStartRequest,
+    DevServerStatus,
+)
+from ..services.dev_server_manager import get_devserver_manager
+from ..services.project_config import (
+    clear_dev_command,
+    get_dev_command,
+    get_project_config,
+    set_dev_command,
+)
+
+# Add root to path for registry import
+_root = Path(__file__).parent.parent.parent
+if str(_root) not in sys.path:
+    sys.path.insert(0, str(_root))
+
+from registry import get_project_path as registry_get_project_path
+
+
+def _get_project_path(project_name: str) -> Path | None:
+    """Get project path from registry."""
+    return registry_get_project_path(project_name)
+
+
+router = APIRouter(prefix="/api/projects/{project_name}/devserver", tags=["devserver"])
+
+
+# ============================================================================
+# Helper Functions
+# ============================================================================
+
+
+def validate_project_name(name: str) -> str:
+    """Validate and sanitize project name to prevent path traversal."""
+    if not re.match(r'^[a-zA-Z0-9_-]{1,50}$', name):
+        raise HTTPException(
+            status_code=400,
+            detail="Invalid project name"
+        )
+    return name
+
+
+def get_project_dir(project_name: str) -> Path:
+    """
+    Get the validated project directory for a project name.
+
+    Args:
+        project_name: Name of the project
+
+    Returns:
+        Path to the project directory
+
+    Raises:
+        HTTPException: If project is not found or directory does not exist
+    """
+    project_name = validate_project_name(project_name)
+    project_dir = _get_project_path(project_name)
+
+    if not project_dir:
+        raise HTTPException(
+            status_code=404,
+            detail=f"Project '{project_name}' not found in registry"
+        )
+
+    if not project_dir.exists():
+        raise HTTPException(
+            status_code=404,
+            detail=f"Project directory not found: {project_dir}"
+        )
+
+    return project_dir
+
+
+def get_project_devserver_manager(project_name: str):
+    """
+    Get the dev server process manager for a project.
+
+    Args:
+        project_name: Name of the project
+
+    Returns:
+        DevServerProcessManager instance for the project
+
+    Raises:
+        HTTPException: If project is not found or directory does not exist
+    """
+    project_dir = get_project_dir(project_name)
+    return get_devserver_manager(project_name, project_dir)
+
+
+# ============================================================================
+# Endpoints
+# ============================================================================
+
+
+@router.get("/status", response_model=DevServerStatus)
+async def get_devserver_status(project_name: str) -> DevServerStatus:
+    """
+    Get the current status of the dev server for a project.
+
+    Returns information about whether the dev server is running,
+    its process ID, detected URL, and the command used to start it.
+    """
+    manager = get_project_devserver_manager(project_name)
+
+    # Run healthcheck to detect crashed processes
+    await manager.healthcheck()
+
+    return DevServerStatus(
+        status=manager.status,
+        pid=manager.pid,
+        url=manager.detected_url,
+        command=manager._command,
+        started_at=manager.started_at,
+    )
+
+
+@router.post("/start", response_model=DevServerActionResponse)
+async def start_devserver(
+    project_name: str,
+    request: DevServerStartRequest = DevServerStartRequest(),
+) -> DevServerActionResponse:
+    """
+    Start the dev server for a project.
+
+    If a custom command is provided in the request, it will be used.
+    Otherwise, the effective command from the project configuration is used.
+
+    Args:
+        project_name: Name of the project
+        request: Optional start request with custom command
+
+    Returns:
+        Response indicating success/failure and current status
+    """
+    manager = get_project_devserver_manager(project_name)
+    project_dir = get_project_dir(project_name)
+
+    # Determine which command to use
+    command: str | None
+    if request.command:
+        command = request.command
+    else:
+        command = get_dev_command(project_dir)
+
+    if not command:
+        raise HTTPException(
+            status_code=400,
+            detail="No dev command available. Configure a custom command or ensure project type can be detected."
+        )
+
+    # Now command is definitely str
+    success, message = await manager.start(command)
+
+    return DevServerActionResponse(
+        success=success,
+        status=manager.status,
+        message=message,
+    )
+
+
+@router.post("/stop", response_model=DevServerActionResponse)
+async def stop_devserver(project_name: str) -> DevServerActionResponse:
+    """
+    Stop the dev server for a project.
+
+    Gracefully terminates the dev server process and all its child processes.
+
+    Args:
+        project_name: Name of the project
+
+    Returns:
+        Response indicating success/failure and current status
+    """
+    manager = get_project_devserver_manager(project_name)
+
+    success, message = await manager.stop()
+
+    return DevServerActionResponse(
+        success=success,
+        status=manager.status,
+        message=message,
+    )
+
+
+@router.get("/config", response_model=DevServerConfigResponse)
+async def get_devserver_config(project_name: str) -> DevServerConfigResponse:
+    """
+    Get the dev server configuration for a project.
+
+    Returns information about:
+    - detected_type: The auto-detected project type (nodejs-vite, python-django, etc.)
+    - detected_command: The default command for the detected type
+    - custom_command: Any user-configured custom command
+    - effective_command: The command that will actually be used (custom or detected)
+
+    Args:
+        project_name: Name of the project
+
+    Returns:
+        Configuration details for the project's dev server
+    """
+    project_dir = get_project_dir(project_name)
+    config = get_project_config(project_dir)
+
+    return DevServerConfigResponse(
+        detected_type=config["detected_type"],
+        detected_command=config["detected_command"],
+        custom_command=config["custom_command"],
+        effective_command=config["effective_command"],
+    )
+
+
+@router.patch("/config", response_model=DevServerConfigResponse)
+async def update_devserver_config(
+    project_name: str,
+    update: DevServerConfigUpdate,
+) -> DevServerConfigResponse:
+    """
+    Update the dev server configuration for a project.
+
+    Set custom_command to a string to override the auto-detected command.
+    Set custom_command to null/None to clear the custom command and revert
+    to using the auto-detected command.
+
+    Args:
+        project_name: Name of the project
+        update: Configuration update containing the new custom_command
+
+    Returns:
+        Updated configuration details for the project's dev server
+    """
+    project_dir = get_project_dir(project_name)
+
+    # Update the custom command
+    if update.custom_command is None:
+        # Clear the custom command
+        try:
+            clear_dev_command(project_dir)
+        except ValueError as e:
+            raise HTTPException(status_code=400, detail=str(e))
+    else:
+        # Set the custom command
+        try:
+            set_dev_command(project_dir, update.custom_command)
+        except ValueError as e:
+            raise HTTPException(status_code=400, detail=str(e))
+        except OSError as e:
+            raise HTTPException(
+                status_code=500,
+                detail=f"Failed to save configuration: {e}"
+            )
+
+    # Return updated config
+    config = get_project_config(project_dir)
+
+    return DevServerConfigResponse(
+        detected_type=config["detected_type"],
+        detected_command=config["detected_command"],
+        custom_command=config["custom_command"],
+        effective_command=config["effective_command"],
+    )