feat: add Pi process and RPC foundation

electron/coding-runtime/pi/process-errors.ts

@@ -0,0 +1,38 @@
+export type PiProcessErrorCode =
+  | 'PI_RPC_PROTOCOL_ERROR'
+  | 'PI_RPC_TIMEOUT'
+  | 'PI_RPC_ABORTED'
+  | 'PI_RPC_RESPONSE_ERROR'
+  | 'PI_RPC_WRITE_FAILED'
+  | 'PI_RPC_EXITED'
+  | 'PI_WORKER_START_FAILED'
+  | 'PI_WORKER_STOPPED'
+  | 'PI_WORKER_STOP_FAILED';
+
+export type PiProcessErrorDetails = {
+  cause?: unknown;
+  generation?: number;
+  diagnostic?: string;
+};
+
+export class PiProcessError extends Error {
+  readonly code: PiProcessErrorCode;
+  readonly generation?: number;
+  readonly diagnostic?: string;
+
+  constructor(
+    code: PiProcessErrorCode,
+    message: string,
+    details: PiProcessErrorDetails = {},
+  ) {
+    super(message, details.cause === undefined ? undefined : { cause: details.cause });
+    this.name = 'PiProcessError';
+    this.code = code;
+    this.generation = details.generation;
+    this.diagnostic = details.diagnostic;
+  }
+}
+
+export function isPiProcessError(error: unknown): error is PiProcessError {
+  return error instanceof PiProcessError;
+}