refactor(connectors): drop dead CLI command field after pi-mono migration

The CLI-adapter era `connector.command` field became vestigial once every
provider dispatch went through pi-ai. The schema still required a non-empty
command, so onboarding saveConnector silently rejected every Pi Mono row
(which carries an empty default). Remove the field from the payload chain
(renderer → IPC schema → DB CRUD → run dispatch → worker job), narrow
RunJob.taskId to match EnqueueRunPayload, and drop the dead helper plus
its test. Schema column stays NOT NULL for DB compatibility; seedConnectors
writes a literal empty string so no migration is needed.

src/shared/types/records-core.ts

@@ -43,7 +43,6 @@ export interface ConnectorRecord {
   label: string;
   description: string;
   status: ConnectorStatus;
-  command: string;
   version: string | null;
   authState: "unknown" | "ok" | "required" | "error";
   lastCheckedAt: string | null;