workspace: remove observation cursor surface

.yoi/tickets/00001KX7838M2/item.md

@@ -1,8 +1,8 @@
 ---
 title: 'Remove worker observation WebSocket cursor surface'
-state: 'inprogress'
+state: 'done'
 created_at: '2026-07-11T00:09:06Z'
-updated_at: '2026-07-11T00:09:33Z'
+updated_at: '2026-07-11T00:31:41Z'
 assignee: null
 queued_by: 'yoi ticket'
 queued_at: '2026-07-11T00:09:32Z'

.yoi/tickets/00001KX7838M2/thread.md

@@ -39,4 +39,37 @@ Ticket を `yoi ticket` が queued にしました。
 State changed to `inprogress`.
 
 
+---
+
+<!-- event: implementation_report author: hare at: 2026-07-11T00:31:41Z -->
+
+## Implementation report
+
+Removed the backend-local worker observation cursor surface.
+
+- Browser-facing worker observation envelopes no longer include `cursor`; they carry runtime/worker identity, runtime event id, and payload.
+- Workspace-server observation proxy no longer owns cursor state, cursor validation, replay state, or store/open methods; it only maps upstream Runtime events to browser envelopes.
+- Workspace-server WS attach ignores no cursor path because no cursor query is accepted/extracted.
+- Backend Runtime client no longer sends cursor query params or deduplicates by backend cursor.
+- Frontend Console no longer stores cursor/lastCursor and projects events by runtime event id.
+
+Validation:
+- cargo test -q -p yoi-workspace-server
+- cargo test -q -p client
+- cd web/workspace && deno task check
+- cd web/workspace && deno task test
+- cargo test -q
+- git diff --check
+- nix build .#yoi --no-link
+
+
+---
+
+<!-- event: state_changed author: "yoi ticket" at: 2026-07-11T00:31:41Z from: inprogress to: done reason: cli_state field: state -->
+
+## State changed
+
+State changed to `done`.
+
+
 ---