[claude] sync-harmony endpoint returns 200 when a project is blocked from syncing

[Claude, autonomous]

POST /api/merge/sync-harmony returns 200 OK even when the project is blocked from syncing, so the caller can't tell that no sync actually happened.

Root cause

SyncHarmonyProject (backend/FwHeadless/Routes/MergeRoutes.cs) calls SyncWorker.ExecuteSync(onlyHarmony: true) but discards the returned SyncJobResult, then unconditionally returns TypedResults.Ok():

var syncWorker = ActivatorUtilities.CreateInstance<SyncWorker>(services, projectId);
await syncWorker.ExecuteSync(stoppingToken, onlyHarmony: true);   // result ignored
return TypedResults.Ok();

ExecuteSync does detect the block and returns SyncJobResult(SyncJobStatusEnum.SyncBlocked, …) (backend/FwHeadless/Services/SyncHostedService.cs), but because the result is thrown away the endpoint still reports success. In the logs the worker logs Project ... is blocked from syncing, and the request immediately finishes 200.

Contrast with the sibling endpoint. ExecuteMergeRequest (/api/merge/execute) checks the same block status up front and returns 423 Locked. sync-harmony should behave consistently.

Impact

The LexBox-side caller FwHeadlessClient.SyncHarmony branches on response.IsSuccessStatusCode. A blocked project returns 200, so the caller treats a skipped sync as a completed one. The sync block is effectively invisible to this code path.

Suggested fix

Map the SyncJobResult to a status code in SyncHarmonyProject (return 423 Locked for SyncJobStatusEnum.SyncBlocked, and surface other non-success statuses like ProjectNotFound / UnableToAuthenticate rather than collapsing them to 200). Extend the response Results<...> union accordingly.

Test: backend/Testing/ApiTests/ProjectBlockingTests.cs is the natural home for a case asserting sync-harmony returns 423 for a blocked project.

Start in backend/FwHeadless/Routes/MergeRoutes.cs at SyncHarmonyProject and compare its response handling with ExecuteMergeRequest. Read SyncHostedService.cs for SyncJobResult statuses, then run the relevant tests in backend/Testing/ApiTests/ProjectBlockingTests.cs. Done means blocked syncs return 423 and other non-success results are not reported as 200.