workspace: stop worker before cleanup delete

.yoi/tickets/00001KXDWAXTS/item.md

@@ -1,8 +1,8 @@
 ---
 title: 'Stop Worker before cleanup deletion'
-state: 'inprogress'
+state: 'done'
 created_at: '2026-07-13T13:58:15Z'
-updated_at: '2026-07-13T13:58:54Z'
+updated_at: '2026-07-13T14:05:35Z'
 assignee: null
 queued_by: 'yoi ticket'
 queued_at: '2026-07-13T13:58:54Z'

.yoi/tickets/00001KXDWAXTS/thread.md

@@ -39,4 +39,45 @@ Ticket を `yoi ticket` が queued にしました。
 State changed to `inprogress`.
 
 
+---
+
+<!-- event: implementation_report author: hare at: 2026-07-13T14:05:35Z -->
+
+## Implementation report
+
+Changed Worker cleanup execution to stop the selected Worker before Runtime deletion.
+
+Root cause:
+- Runtime `delete_worker` rejects active Workers with `worker <id> is running and must be stopped before deletion`.
+- The cleanup plan can present a Worker as cleanup-eligible when the browser-facing projected state is not `running` (for example execution rejected/unconnected) while Runtime status is still active.
+- Cleanup execution previously called Runtime delete directly, causing `workspace_cleanup_worker_runtime_delete_rejected`.
+
+Changes:
+- `cleanup_runtime_worker_for_execution` now calls `stop_worker` first with a cleanup reason.
+- If stop is rejected, the cleanup fails with `workspace_cleanup_worker_runtime_stop_rejected` and preserves Runtime diagnostics.
+- Only after accepted stop does cleanup call Runtime delete and then delete the Backend registry row.
+- Unknown-worker during stop/delete remains idempotent for stale Backend registry cleanup.
+
+Manual observation:
+- Direct Runtime DELETE for worker 1 returned HTTP 400: `worker 1 is running and must be stopped before deletion`.
+- Direct Runtime stop followed by delete succeeded, confirming the required operation sequence.
+
+Validation:
+- `cargo fmt --check`
+- `git diff --check`
+- `cargo check -q`
+- `cargo test -q -p yoi-workspace-server`
+- targeted cleanup execution test
+- `nix build .#yoi --no-link`
+
+
+---
+
+<!-- event: state_changed author: "yoi ticket" at: 2026-07-13T14:05:35Z from: inprogress to: done reason: cli_state field: state -->
+
+## State changed
+
+State changed to `done`.
+
+
 ---