ik suite

Covers the pure-math core of the ik package — chain resolution, the five solvers, and rotation limits. Everything here runs without a rendered frame, a live skeleton, or an entity, so it executes in the offline shard.

What this locks in:

• Chain resolution — root-to-tip ordering, segment lengths and total reach, forward kinematics, and the three ways resolution legitimately fails (tip not a descendant of the root, an unknown bone name, a role the rig does not fill). Also rotateGlobal pivoting a bone about its own joint rather than the chain root, which is the property every solver depends on.
• twoBone — exact reach for targets in every direction around the root, graceful extension toward an unreachable one, weight 0 as an exact pass-through, partial weight landing between the incoming pose and the solve, idempotence across repeated solves, and pole targets producing opposite, deterministic bend planes.
• ccd and fabrik — convergence, early exit at tolerance, segment lengths preserved through the solve, the root staying anchored, and rotation limits holding while iterating.
• aim and lookAt — the tip axis landing on the target direction, the total turn respecting clampAngle, and bodyWeight actually moving the turn down the chain instead of leaving it all on the head.
• Rotation limits — clamping outside the range, leaving values inside it untouched, stability under repeated application (a limit that drifted each frame would slowly collapse a pose), and a hinge stripping off-axis swing.

Idempotence and repeat-application stability appear throughout because IK runs every frame on the result of the previous frame: a solver that drifts by a fraction of a degree per solve looks correct in a single-frame test and visibly wrong after a second of playback.