fix(canvas): close three minor post-review cleanups

- Route verification-read-fails branch through injected out writer so
  cmd_restore_canvas captures all stdout; assert event_id/accepted/message
  in restore_succeeds_when_verification_read_fails.
- Scope pending-guard alert query to the originating <li> and assert
  errorText contains the rejection message; narrow invariant-3 comments
  to match what the test actually exercises (row expand buttons, not the
  Restore action button).
- Update conflict_relay doc block: attempt 1 returns retryable HTTP 503,
  not a dropped TCP connection.

Co-authored-by: Will Pfleger <pfleger.will@gmail.com>
Signed-off-by: Will Pfleger <pfleger.will@gmail.com>

Author: Duncan

crates/buzz-cli/src/commands/channels.rs

@@ -518,7 +518,7 @@ pub async fn cmd_restore_canvas(
             eprintln!(
                 "warning: canvas restore {our_id} was published but its post-write verification read failed; the restore is preserved in history — check `buzz canvas history` if a concurrent edit may have landed"
             );
-            println!("{}", normalize_write_response(&resp));
+            let _ = writeln!(out, "{}", normalize_write_response(&resp));
             return Ok(());
         }
     };
@@ -3819,13 +3819,28 @@ mod restore_canvas_tests {
     #[tokio::test]
     async fn restore_succeeds_when_verification_read_fails() {
         let (url, submitted, _) = relay(PostHead::ReadFails).await;
-        cmd_restore_canvas(&client(&url), CHANNEL, REVISION, &mut vec![])
+        let mut out = vec![];
+        cmd_restore_canvas(&client(&url), CHANNEL, REVISION, &mut out)
             .await
             .expect("an accepted restore whose verification read fails still succeeds");
         assert!(
             submitted.lock().unwrap().is_some(),
             "the restore did publish before the verification read failed"
         );
+        let json: serde_json::Value = serde_json::from_slice(&out)
+            .expect("stdout must be valid JSON even when verification read fails");
+        assert!(
+            json.get("event_id").is_some(),
+            "stdout JSON must contain event_id"
+        );
+        assert!(
+            json.get("accepted").is_some(),
+            "stdout JSON must contain accepted"
+        );
+        assert!(
+            json.get("message").is_some(),
+            "stdout JSON must contain message"
+        );
     }
 
     /// `restore` sends `"consistency": "strong"` on the write-influencing
@@ -3888,8 +3903,8 @@ mod restore_canvas_tests {
     /// seam in `submit_stored_event`:
     ///
     /// 1. Attempt 1 — POST /events: A is persisted on the relay; the relay then
-    ///    drops the TCP connection (no response body) so `with_retry_body` sees a
-    ///    network/body error and retries with the same bytes.
+    ///    returns HTTP 503 (a retryable status), so `with_retry_body` retries
+    ///    with the same bytes.
     /// 2. A concurrent writer B (built on A) arrives and becomes the new head
     ///    with `expected-revision = A`.
     /// 3. Attempt 2 — POST /events: returns the canonical 409 conflict body

desktop/src/features/channels/ui/CanvasRestorePendingGuard.test.mjs

@@ -12,7 +12,8 @@
  *    the originating row, and `set_canvas` was called exactly once.
  * 3. **No spurious second dispatch**: attempting another restore while the
  *    mutation is pending (before the rejection settles) does not fire a second
- *    `set_canvas` call — the Restore button also carries `disabled` while pending.
+ *    `set_canvas` call — the row expand buttons also carry `disabled` while
+ *    pending, preventing `reset()` from being called mid-flight.
  *
  * Revert-causality: removing `disabled={restoreMutation.isPending}` from the
  * row button un-disables the row during the pending phase. In that case the
@@ -65,7 +66,7 @@ let CommunitiesProvider;
 let CanvasHistoryPanel;
 
 // Controls the IPC: null means the test has not triggered set_canvas yet.
-let deferredResolve = null;
+let _deferredResolve = null;
 let deferredReject = null;
 let setCanvasCalls = 0;
 
@@ -101,7 +102,7 @@ before(async () => {
       if (cmd === "set_canvas") {
         setCanvasCalls += 1;
         return new Promise((resolve, reject) => {
-          deferredResolve = resolve;
+          _deferredResolve = resolve;
           deferredReject = reject;
         });
       }
@@ -162,15 +163,15 @@ async function settle(iterations = 8) {
 /**
  * Full pending-guard contract:
  *
- * 1. Row buttons are disabled while restoreMutation.isPending is true.
+ * 1. Row expand buttons are disabled while restoreMutation.isPending is true.
  * 2. Rejecting the IPC makes the error visible under the originating row;
  *    set_canvas remains at exactly 1 call (no reset() fired mid-flight).
- * 3. Clicking the Restore button while pending does not fire a second IPC
- *    (the Restore button also carries disabled={restoreMutation.isPending}).
+ * 3. Clicking another row's expand button while pending does not fire a second
+ *    IPC (disabled prevents reset() from being called mid-flight).
  */
 test("pending-guard: row disabled, rejection visible, no second dispatch", async () => {
   setCanvasCalls = 0;
-  deferredResolve = null;
+  _deferredResolve = null;
   deferredReject = null;
 
   const client = new QueryClient({
@@ -254,8 +255,10 @@ test("pending-guard: row disabled, rejection visible, no second dispatch", async
   });
   await settle(12);
 
-  // After rejection the error must render under the OLDER_A row.
-  const errorEl = container.querySelector("[role='alert']");
+  // After rejection the error must render under the OLDER_A row (the
+  // originating row — OLDER_A was selected when set_canvas was dispatched).
+  const olderALi = items[1]?.closest("li");
+  const errorEl = olderALi?.querySelector("[role='alert']") ?? null;
   const errorVisible = errorEl !== null;
   const errorText = errorEl?.textContent ?? "";
 
@@ -284,6 +287,10 @@ test("pending-guard: row disabled, rejection visible, no second dispatch", async
       errorVisible,
       "rejecting the IPC must render an error under the originating row",
     );
+    assert.ok(
+      errorText.includes(rejectionMessage),
+      `error text must contain the rejection message; got: "${errorText}"`,
+    );
     assert.equal(
       finalCallCount,
       1,