docs(15): write the missing 15-04 summary, closing Phase 15

The AD group membership sync shipped on 2026-08-04 as 614de28; only its
summary was never written, which left Phase 15 sitting at 7/8 as if work were
outstanding. Nothing was.

Each promise the plan made is checked against today's source rather than
against the commit message: bound-only selection, no second sync job, deletion
restricted to source LDAP, manual memberships preserved, memberOf reverse query
instead of attribute reads, RFC-4515 escaping of the group DN, no nested-group
resolution, order independence, per-group error isolation. The 2026-08-11 sync
run on alpha additionally exercised this path against a real directory.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

.planning/STATE.md

@@ -8,12 +8,12 @@ status: complete
 stopped_at: Phase 16 abgeschlossen — UAT durchgefuehrt, kritischer Sweep-Fehler gefunden und behoben (260811-f9i), Rest-Annahme A1 bewusst als offen akzeptiert
 last_updated: "2026-08-11T09:25:00.000Z"
 last_activity: 2026-08-11
-last_activity_desc: DOE-Bekanntmachungslinks repariert (260811-j04)
+last_activity_desc: Phase 15 geschlossen (Bericht 15-04 nachgezogen)
 progress:
   total_phases: 16
   completed_phases: 15
   total_plans: 80
-  completed_plans: 78
+  completed_plans: 79
 ---
 
 # Project State