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/renderer/components/company-onboarding/useConnectorCallbacks.ts

@@ -22,7 +22,6 @@ export function useConnectorCallbacks(connectors: ProfileSnapshot["connectors"])
     try {
       unwrap(await window.agentCompany.saveConnector({
         id: connectorId as ConnectorId,
-        command: connector.command,
         model,
         envBindingText,
         notes: notes ?? connector.notes,