fix(test): repair the teardown suite the union broke

Cherry-picked from 46ad377ceb with the relay half dropped: that commit
also repaired relay-concurrency-policy-flip-mid-mint.test.ts, which does
not exist on this PR and belongs with the relay cluster's own branch.

The handle-gap half is what this PR needs. Neither break was visible on
its own branch -- both only appear once the verdict rules compose.

src/renderer/src/lib/host-mirror-handle-gap-teardown.test.ts

@@ -26,9 +26,15 @@ const WORKTREE_ID = 'repo-1::/workspace/repo'
 const initialAppStoreState = useAppStore.getState()
 
 function parkAndExpire(environmentId: string, tabId: string): void {
+  // Rows ACCUMULATE. Replacing them would unpublish the panes parked earlier, and the tab-death
+  // rule would then legitimately sweep their verdicts before teardown was ever reached — this
+  // suite is about a class no recording-driven prune can reach, so every pane here stays live.
+  const published = useAppStore.getState().tabsByWorktree[WORKTREE_ID] ?? []
   useAppStore.setState({
     ptyIdsByTabId: {},
-    tabsByWorktree: { [WORKTREE_ID]: [{ id: tabId, title: tabId }] }
+    tabsByWorktree: {
+      [WORKTREE_ID]: [...published.filter((tab) => tab.id !== tabId), { id: tabId, title: tabId }]
+    }
   } as never)
   parkUntilHostMirrorHandleLands(environmentId, WORKTREE_ID, tabId, () => {})
   vi.advanceTimersByTime(HOST_MIRROR_HANDLE_GAP_DEADLINE_MS)

src/renderer/src/lib/host-mirror-handle-gap-wait.ts

@@ -47,13 +47,21 @@ const waitersByPane = new Map<string, HandleGapWaiter>()
 /**
  * Connection generation whose wait already expired for the pane.
  *
- * Two rules drain it, and neither subsumes the other because both are driven by a recording:
- * `recordExpiredWait` drops rows from a superseded generation, and a separate rule (8f166411306)
- * drops rows whose tab is no longer published, both scoped to the environment doing the recording.
- * An environment that is REMOVED records nothing ever again, so neither rule can reach it — hence
- * the teardown clear below, which is the only thing that can. A stranded row is inert (removing an
- * environment advances its connection generation, so it can never match again); this is a leak
- * fix, not a correctness one.
+ * THREE drains, with three different triggers. Getting the scopes right is the whole design; see
+ * `recordExpiredWait` for why the first two must NOT share a scope.
+ *  - superseded generation: per key, EVERY environment. Runs on any recording, anywhere.
+ *  - dead tab row: the recording environment ONLY. Runs on a recording in that environment.
+ *  - removed environment: `clearHostMirrorHandleGapVerdictsForEnvironment`, on teardown. The only
+ *    trigger that fires at all for an environment that will never record again. A row stranded
+ *    there is inert — removal advances the generation, so it can never match — so that one is a
+ *    leak fix, not a correctness fix.
+ *
+ * ONE CLASS IS STILL UNCOVERED, and unlike the rest it is NOT conservative: a retracted tab id
+ * that is republished inherits the old pane's verdict and skips its own wait, which is the #19735
+ * direction rather than a longer hold. No trigger above reaches it — the dead-row predicate stops
+ * matching once the id is live again, teardown is the wrong event, and a pane holding a verdict
+ * never parks, so no waiter observes the retraction. Closing it needs a fourth trigger, on row
+ * retraction. Pinned in host-mirror-handle-gap-verdict-union.test.ts; do not delete that case.
  */
 const expiredGenerationByPane = new Map<string, number>()
 let unsubscribeStore: (() => void) | null = null