docs(ai): list all three embeddable clauses in int-spec header; drop tautological assert (F14,F15)

F14: the lockstep int-spec header still described the pre-F6 two-clause set with
     'iff' — add the content-JSON text-node clause so it matches embeddablePredicate.
F15: remove the redundant expect(ttl).toBeLessThanOrEqual(120) that followed
     expect(ttl).toBe(120).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/server/src/integrations/ai/ai-settings.service.spec.ts

@@ -186,7 +186,6 @@ describe('AiSettingsService.reindex progress seed', () => {
     // pinned to the client poll cap (120s) so a still-pending run can't expire
     // into a false "done" while the client is still polling (F11).
     expect(ttl).toBe(120);
-    expect(ttl).toBeLessThanOrEqual(120);
     expect(aiQueue.add).toHaveBeenCalledTimes(1);
     // Seed must precede the enqueue so the first poll already reports done=0.
     expect(order).toEqual(['start', 'add']);