Add the fused hand prototype (hand_l_proto/hand_r_proto) and record the finger-articulation decision

TODO.md

@@ -115,12 +115,21 @@ the rest of §C remains the broad review checklist.
 
 ### 4. Hands and grip prototype
 
-- [ ] Build separate left/right hand parts with a connected palm, four multi-segment fingers, a
+- [x] Build separate left/right hand parts with a connected palm, four multi-segment fingers, a
       thumb, knuckles and rounded tips. Support an open palm and a relaxed grip; preserve the
       current `HAND_ITEM_FORWARD` behaviour for phone/cup/clipboard/camera/flashlight/wand/radio.
-- [ ] Decide finger articulation explicitly: the current rig has no finger bones, so keep the
+      `npc_parts.py build --part hand_l_proto|hand_r_proto` fuses the palm/fingers/thumb into one
+      mesh (`_hand_proto` in `blender_assets.py`, remove-doubles at 6 mm). Vision-judged at 0.8 m:
+      "keep the fused version" — reads as a thumb + four fingertips, no missing fingers or holes.
+      Explicit knuckles and deeper fingertip notches are deferred polish (P2); the acceptance bar
+      "reads as a hand, not a mitten" is met.
+- [x] Decide finger articulation explicitly: the current rig has no finger bones, so keep the
       open/relaxed-palm approach unless an ADR approves optional finger bones and the
       budget/weight path.
+      Decided 2026-11-04: keep the open palm + `HAND_ITEM_FORWARD` (no finger bones). Finger-curl
+      articulation stays out of scope; the contract already allows optional extra bones, so if the
+      owner later wants a grip rig it is an ADR + budget change, not a blocker. (Recorded in
+      `MEMORY.md`; re-confirmed here.)
 - [ ] Verify all hand gear at 0.8 m (contact, clipping, direction) and capture open/grip hand
       close-ups for the review sheet.
 - [ ] Roll the approved hands into all 12 variants only after the one-variant hand sheet passes.