feat(transport): introduce transport abstraction and socket-mode support for RustBridge

ts/interfaces/transport.ts

@@ -0,0 +1,26 @@
+import type * as plugins from '../plugins.js';
+
+/**
+ * Abstract transport for communicating with a Rust process.
+ * Both stdio and socket transports implement this interface.
+ *
+ * Events emitted:
+ * - 'line' (line: string) — a complete newline-terminated JSON line received
+ * - 'error' (err: Error) — transport-level error
+ * - 'close' (...args: any[]) — transport has closed/disconnected
+ * - 'stderr' (line: string) — stderr output (stdio transport only)
+ * - 'reconnected' () — transport reconnected after unexpected disconnect (socket only)
+ */
+export interface IRustTransport extends plugins.events.EventEmitter {
+  /** Connect the transport (spawn process or connect to socket). Resolves when I/O channel is open. */
+  connect(): Promise<void>;
+
+  /** Write a string to the transport. Handles backpressure. */
+  write(data: string): Promise<void>;
+
+  /** Disconnect the transport. For stdio: kills the process. For socket: closes the connection. */
+  disconnect(): void;
+
+  /** Whether the transport is currently connected and writable. */
+  readonly connected: boolean;
+}