fix(puppet): v0.4.2 — per-channel write_bone conflict (was per-track)

Allow procedural callbacks to write channels that no active anim
writes on the same bone. Example: walk_anim writes leg.scl; procedural
can now write leg.rot without track-conflict error. Previously the
guard was track-level (any anim on the track blocked ALL writes).

Enables hip-anchor-stable + leg-orientation-procedural pattern in
vagrant-skeleton (legs parent=body for body-relative hips, leg.rot
overridden per-frame to walk-direction while walk_fwd_lower drives
leg.scl).

Existing Group 4 track-conflict test still passes: walk_anim writes
leg.rot in keyframes; procedural-write of leg.rot still errors (same
channel). 42/42 assertions GREEN.

manifest.lib

@@ -1,6 +1,6 @@
 {
     "id": "lib-core.puppet",
-    "version": "0.4.1",
+    "version": "0.4.2",
     "api_min": "0.1",
     "deps": []
 }