Flaky CI Failure: xdbg Docker build broken — mismatched types after GroupId refactor

## Flaky CI Failure: xdbg Docker build broken — mismatched types after GroupId refactor **Workflow:** Push XDBG Image **Failed run:** https://github.com/xmtp/libxmtp/actions/runs/25116683062 **Commit:** e87c081fc045b2d69c0bdcdaeb7ea33c3435a711 **Failed jobs:** Build and push xdbg image ### Summary The Docker build for the `xdbg` image fails with a Rust compilation error (`E0308: mismatched types`) in `apps/xmtp_debug/src/app/generate/groups.rs:217`. The refactor in commit `e87c081` (`refactor(xmtp_mls): MlsGroup.group_id holds GroupId (Task 6)`) changed the return type of `group_id` from `Vec<u8>` to `xmtp_proto::types::GroupId`, but the `xdbg` app was not updated to match. The build will deterministically fail on every run until this is fixed. The compiler suggests the fix: `group_id.to_vec()`. ### Error Details ``` error[E0308]: mismatched types --> apps/xmtp_debug/src/app/generate/groups.rs:217:9 | 217 | Ok((group_id, create_secs)) | ^^^^^^^^ expected `Vec<u8>`, found `GroupId` | = note: expected struct `Vec<u8>` found struct `xmtp_proto::types::GroupId` help: try using a conversion method | 217 | Ok((group_id.to_vec(), create_secs)) | +++++++++ error: could not compile `xdbg` (bin "xdbg") due to 1 previous error ERROR: failed to build: failed to solve: process "/bin/sh -c cargo build --release --package xdbg" did not complete successfully: exit code: 101 ``` ### Analysis This is a **code failure**, not an infrastructure failure. The refactor PR #3577 updated `MlsGroup.group_id` to return `GroupId` instead of `Vec<u8>` across `xmtp_mls`, but the `xdbg` debug application at `apps/xmtp_debug/src/app/generate/groups.rs:217` was missed. The fix is straightforward: call `.to_vec()` on `group_id` (or update the surrounding code to work with `GroupId` directly) in that file. This will fail every Docker image push until resolved. --- *Reported by [Flaky Failure Watcher](https://github.com/xmtp/libxmtp/blob/main/.github/workflows/flaky-failure-watcher.yml)*