Pass create-key workspace_id (from OPENROUTER_WORKSPACE_ID, defaulting to the
project workspace) so minted keys land in the intended workspace instead of the
management key's default. Rename key to non-PII llmapikey/gh-<id>.
- buildCreateKeyBody emits workspace_id only when set (omission keeps default).
- createKey threads workspaceId; mintAndPersist sources it from env.
- Test asserts workspace_id presence/omission; document the new env var.