feat(rig lab): wrists in three axes, and sliders that belong to the pose on screen

Three things the lab could not do.

WRISTS. Each hand had one scalar, a twist about the barrel. That is the only
axis a hand wrapping a cylinder is free in ONCE the arc onto the barrel is
solved — which is true of the support hand, was never true of the trigger hand,
and in neither case left a way to cock a wrist forward or break it inward. Both
now take pitch, yaw and roll, applied in the GUN's frame so the three sliders
mean the same thing whether the muzzle is down at low ready or level down the
sights. Zero is exactly the old behaviour, since the roll term defaulted to zero
too.

HAND POINTS. `gun_stock` and `gun_fore` are the distances along the weapon at
which each hand sits, and they were labelled by what they measure rather than by
whose hand it is. They now say TRIGGER and SUPPORT, next to the off-barrel
shifts for the same two hands, so the four controls that place a hand read as
four controls that place a hand.

POSES. The hold's knobs are now per pose, and the lab shows one pose's at a
time. Half of them mean something different at low ready than down the sights;
showing both sets at once meant every slider on screen was for one of two poses
with nothing saying which. Selecting a pose rebuilds the panel.

Two poses, not four, and deliberately: the runtime blends between exactly two
holds on `ads`. Running and Crouched are locomotion states that still use the
low-ready hold, so they edit the same numbers — and the heading says so, rather
than letting someone tune "Running" and wonder why standing still changed.
Offering four independent tunings would be inventing a capability the code does
not have, and the fourth would silently do nothing.

`pitch` is the case that forced the design: down the sights the muzzle follows
the CAMERA, so there is nothing there to tune. It exists at low ready and
nowhere else, and a spec table where a knob names the poses it applies to is
what lets that be said instead of shipping a control that does nothing.

hold_pose_check asserts both halves — that no pose shows another's knobs, that
aiming offers no muzzle pitch, that the heading names the hold being edited, and
that all twelve wrist axes turn the hand they name.

Its first version reported every wrist axis as moving the hand by 0.0 degrees,
which is precisely the answer it would have given if the wrists had never been
implemented: it read `get_bone_pose_rotation` from a SceneTree script, and Godot
restores every bone's local pose after the modifier pass. The repo has a
reference section about exactly this and it still cost a cycle. Measured through
a PoseProbe, every axis turns its hand ~20 degrees.

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

.claude/skills/character-pipeline/SKILL.md

@@ -132,7 +132,21 @@ godot --path . res://debug/rig_lab.tscn
 ```
 
 Pick a character, a weapon, a pose or a single clip. Drag sliders for the HOLD
-(character + weapon) and the ANCHORS (character), and save. Click a surface class
+(character + weapon) and the ANCHORS (character), and save.
+
+**The HOLD is per pose.** The runtime blends between exactly two holds, on
+`ads`, so the lab offers two: low ready and aiming. Selecting a pose rebuilds
+the hold sliders to that pose's — you never see a control belonging to the pose
+you are not adjusting. Running and Crouched use the low-ready hold, and the
+heading says so rather than letting someone tune "Running" and wonder why
+standing still changed. `pitch` exists at low ready only: down the sights the
+muzzle follows the camera, so there is nothing there to tune, and a slider that
+does nothing is worse than a missing one.
+
+Knobs that describe the WEAPON and the hands on it — where each hand sits along
+it and off its barrel line, the finger curls, the weapon size — are shared,
+because shouldering a gun does not move the hand along it. Both wrists take
+pitch, yaw and roll in the gun's own frame, per pose. Click a surface class
 to isolate it — that is how the classifier gets checked: click `hair` and
 anything else still standing was misclassified.