Dispatch queued messages written by other processes (#39034)

## Why

Durable thread queues can be updated through another SQLite connection, but loaded idle threads need to notice those updates before they can dispatch the new messages.

## What changed

- Track a durable revision for each thread queue, including backfilling existing queues and updating revisions on inserts, updates, and deletes.
- Poll SQLite's data version and query revisions to find changed queues for loaded threads.
- Wake idle threads with pending external messages, discover queued work when threads are loaded or resumed, and retry each thread independently so one blocked queue does not stall others.

## Testing

- Cover cross-runtime queue writes, edits, independent dispatch, wake retries, and resumed threads.
- Cover migration backfills and revision tracking for queue updates and deletes.

GitOrigin-RevId: 906d902bbf6a760be206a1b2c08fd71427b63c46

codex-rs/state/queue_migrations/0002_queued_thread_revisions.sql

@@ -0,0 +1,34 @@
+CREATE TABLE queued_thread_revisions (
+    revision INTEGER PRIMARY KEY AUTOINCREMENT,
+    thread_id TEXT NOT NULL UNIQUE
+);
+
+INSERT INTO queued_thread_revisions (thread_id)
+SELECT DISTINCT thread_id FROM queued_items ORDER BY thread_id;
+
+CREATE TRIGGER queued_items_revision_after_insert
+AFTER INSERT ON queued_items
+BEGIN
+    INSERT INTO queued_thread_revisions (thread_id)
+    VALUES (NEW.thread_id)
+    ON CONFLICT(thread_id) DO UPDATE
+    SET revision = (SELECT COALESCE(MAX(revision), 0) + 1 FROM queued_thread_revisions);
+END;
+
+CREATE TRIGGER queued_items_revision_after_update
+AFTER UPDATE ON queued_items
+BEGIN
+    INSERT INTO queued_thread_revisions (thread_id)
+    VALUES (NEW.thread_id)
+    ON CONFLICT(thread_id) DO UPDATE
+    SET revision = (SELECT COALESCE(MAX(revision), 0) + 1 FROM queued_thread_revisions);
+END;
+
+CREATE TRIGGER queued_items_revision_after_delete
+AFTER DELETE ON queued_items
+BEGIN
+    INSERT INTO queued_thread_revisions (thread_id)
+    VALUES (OLD.thread_id)
+    ON CONFLICT(thread_id) DO UPDATE
+    SET revision = (SELECT COALESCE(MAX(revision), 0) + 1 FROM queued_thread_revisions);
+END;