chore(characters): regenerate every sidecar with the finger table

The finger roles only reach the runtime through <model>.rig.json, so a
character whose sidecar predates them keeps flat, open hands however good
the pose layer is. Aria, Momo, Miku and the Mannequin re-imported; all six
skins now carry 10 finger chains.

Verified on the Mannequin, which is untextured and so the clearest
diagnostic of the three checked: stock at the shoulder, trigger hand on the
grip, support hand out on the handguard, both fists closed, arms not
crossing. Its arm is a full 0.524 m against Taila's 0.468 and it scales the
weapon independently — 0.231 m of hand separation against her 0.217 — with
the slide-back loop never firing on either.

Known remaining: the support hand's wrist roll leaves the hand hanging a
little under the handguard rather than wrapping it squarely. The grip
POSITION is right on every character; it is the roll about the barrel that
wants another pass.

Co-Authored-By: Claude Opus 5 <[email protected]>

assets/characters/skins/aria.rig.json

@@ -11,21 +11,73 @@
     ],
     "shoulder.R": "Right shoulder",
     "shoulder.L": "Left shoulder",
-    "foot.L": "Left ankle",
     "foot.R": "Right ankle",
-    "hand.R": "Right wrist",
+    "foot.L": "Left ankle",
     "hand.L": "Left wrist",
+    "hand.R": "Right wrist",
     "forearm.R": "Right elbow",
     "forearm.L": "Left elbow",
     "shin.L": "Left knee",
     "shin.R": "Right knee",
     "toe.R": "Right toe",
     "toe.L": "Left toe",
-    "upper_arm.R": "Right arm",
     "upper_arm.L": "Left arm",
+    "upper_arm.R": "Right arm",
     "thigh.L": "Left leg",
     "thigh.R": "Right leg"
   },
+  "fingers": {
+    "thumb.L": [
+      "Thumb0_L",
+      "Thumb1_L",
+      "Thumb2_L"
+    ],
+    "index.L": [
+      "IndexFinger1_L",
+      "IndexFinger2_L",
+      "IndexFinger3_L"
+    ],
+    "middle.L": [
+      "MiddleFinger1_L",
+      "MiddleFinger2_L",
+      "MiddleFinger3_L"
+    ],
+    "ring.L": [
+      "RingFinger1_L",
+      "RingFinger2_L",
+      "RingFinger3_L"
+    ],
+    "pinky.L": [
+      "LittleFinger1_L",
+      "LittleFinger2_L",
+      "LittleFinger3_L"
+    ],
+    "thumb.R": [
+      "Thumb0_R",
+      "Thumb1_R",
+      "Thumb2_R"
+    ],
+    "index.R": [
+      "IndexFinger1_R",
+      "IndexFinger2_R",
+      "IndexFinger3_R"
+    ],
+    "middle.R": [
+      "MiddleFinger1_R",
+      "MiddleFinger2_R",
+      "MiddleFinger3_R"
+    ],
+    "ring.R": [
+      "RingFinger1_R",
+      "RingFinger2_R",
+      "RingFinger3_R"
+    ],
+    "pinky.R": [
+      "LittleFinger1_R",
+      "LittleFinger2_R",
+      "LittleFinger3_R"
+    ]
+  },
   "chains": [
     {
       "class": "breast",