Close and archive the 0.9.9 milestone, record that the upstream clips stay unused, and harden the fallback test

docs/adr/0018-quaternius-stage2-runtime-rig.md

@@ -36,8 +36,10 @@ option 2). The mesh is not proportion-warped: it keeps its source LOD (3,199 wel
 - `NpcAvatar` maps the Quaternius joint names instead of the 13-core names.
 - Gear attach points are re-derived from the Quaternius skeleton (hip ≈0.87, shoulder ≈0.148/1.39,
   wrist ≈0.99, knee ≈0.52).
-- The Quaternius Idle and Walk clips are used directly — they are authored for the 62-joint rig,
-  so no retargeting pass is needed. Combat/gun/sword clips stay unused.
+- The 24 upstream clips ship as authoring reference only and are **not played at runtime**.
+  `NpcAvatar._animate()` drives the proxy pivots and `_sync_skeleton()` writes the bone poses, which
+  is what the FSM already needed for sitting, raising a hand and turning the head. Playing the clips
+  would replace that state machine rather than supplement it; revisiting this needs its own ADR.
 
 Option 1 (keep the 13-core names with Quaternius rest positions) is rejected in favour of the
 full source rig.