fix(sync): route sessions by server-confirmed directory, unstick queued sends

Session directory resolution had no precedence contract: the selection-time
directory short-circuited every lookup, and a persisted runtime value was
consulted before the authoritative record. A worktree session selected before
its directory store bootstrapped kept the active-directory fallback, and that
guess was persisted, so it survived reloads and restarts.

Directory resolution now lives in one module and orders sources by whether the
server confirmed the path, not by whether the value is local or synced:
authoritative (the child store that holds the session) > server-confirmed
selection > worktree attachment/metadata (the requested path, pre-canonical) >
remembered. A guessed selection is no longer persisted, remembered, or ranked.
Chips read the same resolution the composer used, so queue keys cannot diverge.

Queued auto-send could strand an item indefinitely: backoff, missing send
configuration, and the recent-abort window all returned without scheduling a
wake-up, so the queue only retried when an unrelated status or directory change
re-ran the effect. A retry scheduler now wakes it at the earliest known time.

A rejected send rolls the optimistic message back while the composer stays
silent for transport failures, which makes it indistinguishable from nothing
happening. Failures are now recorded to a bounded in-memory log surfaced in the
About diagnostics report, alongside a directory-resolution breakdown, plus
__opencodeDebug.diagnoseSessionDirectory() and getRecentSendFailures().

Prompted by a report of worktree prompting silently failing. That failure was
not reproduced locally, so the diagnostics are what will identify it.

packages/ui/src/hooks/useQueuedMessageAutoSend.test.ts

@@ -29,12 +29,61 @@ mock.module('@/sync/session-ui-store', () => ({
 
 import {
   buildQueuedAutoSendPayload,
+  createQueuedAutoSendRetryScheduler,
   getQueuedAutoSendRetryDelayMs,
   isQueuedAutoSendBackedOff,
   sendQueuedAutoSendPayload,
   shouldDispatchQueuedAutoSend,
 } from './useQueuedMessageAutoSend';
 
+describe('queued auto-send retry scheduler', () => {
+  test('wakes the queue when backoff expires', () => {
+    const callbacks = new Map<number, () => void>();
+    let nextTimer = 0;
+    let wakeups = 0;
+    const scheduler = createQueuedAutoSendRetryScheduler(
+      () => { wakeups += 1; },
+      () => 1_000,
+      (callback, delay) => {
+        callbacks.set(++nextTimer, callback);
+        expect(delay).toBe(500);
+        return nextTimer as unknown as ReturnType<typeof setTimeout>;
+      },
+      (timer) => { callbacks.delete(timer as unknown as number); },
+    );
+
+    scheduler.schedule(1_500);
+    expect(callbacks.size).toBe(1);
+    callbacks.values().next().value?.();
+    expect(wakeups).toBe(1);
+  });
+
+  test('keeps the earliest retry and cancels it on dispose', () => {
+    const callbacks = new Map<number, () => void>();
+    let nextTimer = 0;
+    const delays: number[] = [];
+    const scheduler = createQueuedAutoSendRetryScheduler(
+      () => undefined,
+      () => 1_000,
+      (callback, delay) => {
+        callbacks.set(++nextTimer, callback);
+        delays.push(delay);
+        return nextTimer as unknown as ReturnType<typeof setTimeout>;
+      },
+      (timer) => { callbacks.delete(timer as unknown as number); },
+    );
+
+    scheduler.schedule(3_000);
+    scheduler.schedule(4_000);
+    scheduler.schedule(2_000);
+
+    expect(delays).toEqual([2_000, 1_000]);
+    expect(callbacks.size).toBe(1);
+    scheduler.dispose();
+    expect(callbacks.size).toBe(0);
+  });
+});
+
 describe('shouldDispatchQueuedAutoSend', () => {
   test('dispatches only after an active session becomes idle', () => {
     expect(shouldDispatchQueuedAutoSend('busy', 'idle', false)).toBe(true);