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/schemas.py

@@ -308,3 +308,61 @@ class SettingsUpdate(BaseModel):
         if v is not None and v not in VALID_MODELS:
             raise ValueError(f"Invalid model. Must be one of: {VALID_MODELS}")
         return v
+
+
+# ============================================================================
+# Dev Server Schemas
+# ============================================================================
+
+
+class DevServerStartRequest(BaseModel):
+    """Request schema for starting the dev server."""
+    command: str | None = None  # If None, uses effective command from config
+
+
+class DevServerStatus(BaseModel):
+    """Current dev server status."""
+    status: Literal["stopped", "running", "crashed"]
+    pid: int | None = None
+    url: str | None = None
+    command: str | None = None
+    started_at: datetime | None = None
+
+
+class DevServerActionResponse(BaseModel):
+    """Response for dev server control actions."""
+    success: bool
+    status: Literal["stopped", "running", "crashed"]
+    message: str = ""
+
+
+class DevServerConfigResponse(BaseModel):
+    """Response for dev server configuration."""
+    detected_type: str | None = None
+    detected_command: str | None = None
+    custom_command: str | None = None
+    effective_command: str | None = None
+
+
+class DevServerConfigUpdate(BaseModel):
+    """Request schema for updating dev server configuration."""
+    custom_command: str | None = None  # None clears the custom command
+
+
+# ============================================================================
+# Dev Server WebSocket Message Schemas
+# ============================================================================
+
+
+class WSDevLogMessage(BaseModel):
+    """WebSocket message for dev server log output."""
+    type: Literal["dev_log"] = "dev_log"
+    line: str
+    timestamp: datetime
+
+
+class WSDevServerStatusMessage(BaseModel):
+    """WebSocket message for dev server status changes."""
+    type: Literal["dev_server_status"] = "dev_server_status"
+    status: Literal["stopped", "running", "crashed"]
+    url: str | None = None