fix: v0.12.1 — ISS-001 time-scale slider no longer snaps back to the stale value on speed change (optimistic scale kept until a snapshot confirms it); sim-control commit machinery hardened (synchronous busy ref, in-flight queue flush loop, sent/queued/failed outcomes so queued commits never drop the display)

components/left-pane.test.ts

@@ -0,0 +1,24 @@
+import { describe, expect, it } from 'vitest';
+import { pendingScaleConfirmed } from './LeftPane';
+
+// ISS-001 — the optimistic slider value is cleared exactly when a rendered snapshot confirms
+// it (server scale === pending), never earlier. Clearing at commit time would snap the pointer
+// back to the stale scale for one poll cycle, then jump forward again on the confirming snapshot.
+
+describe('pendingScaleConfirmed', () => {
+  it('is false while there is no pending value', () => {
+    expect(pendingScaleConfirmed(null, 1)).toBe(false);
+    expect(pendingScaleConfirmed(null, 64)).toBe(false);
+  });
+
+  it('stays false while the server still reports the stale scale (the ISS-001 window)', () => {
+    // User committed 64×; the last rendered snapshot is still at 1× → must NOT clear yet.
+    expect(pendingScaleConfirmed(64, 1)).toBe(false);
+    expect(pendingScaleConfirmed(32, 8)).toBe(false);
+  });
+
+  it('becomes true exactly when a snapshot carries the pending scale', () => {
+    expect(pendingScaleConfirmed(64, 64)).toBe(true);
+    expect(pendingScaleConfirmed(1, 1)).toBe(true); // committing the current value confirms immediately
+  });
+});