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.

init.lua

@@ -582,13 +582,33 @@ function M.write_bone(handle, bone_id, values)
     end
     local track_id = p.rig.bone_to_track[bone_id]
     if track_id ~= nil then
-        -- Only check track-conflict if bone is in a track.
+        -- v0.4.2: Per-channel conflict check (was per-track). Allow procedural
+        -- to write channels that no active anim writes on this bone (e.g.,
+        -- walk_anim writes leg.scl while procedural writes leg.rot — disjoint).
+        local writing = {}
+        if values.rot ~= nil then writing.rot = true end
+        if values.pos ~= nil then writing.pos = true end
+        if values.scl ~= nil then writing.scl = true end
         for anim_id, _ in pairs(p.playing) do
             local anim = p.animations[anim_id]
             if anim and anim.track == track_id then
+                for _, kf in ipairs(anim.keyframes) do
+                    local bkf = kf.bones[bone_id]
+                    if bkf then
+                        if writing.rot and bkf.rot ~= nil then
                             error("puppet.write_bone: bone '" .. bone_id
-                      .. "' is on track '" .. track_id
+                                  .. "' channel 'rot' conflicts with anim '" .. anim_id .. "'")
-                      .. "' currently active by keyframe '" .. anim_id .. "'")
+                        end
+                        if writing.pos and bkf.pos ~= nil then
+                            error("puppet.write_bone: bone '" .. bone_id
+                                  .. "' channel 'pos' conflicts with anim '" .. anim_id .. "'")
+                        end
+                        if writing.scl and bkf.scl ~= nil then
+                            error("puppet.write_bone: bone '" .. bone_id
+                                  .. "' channel 'scl' conflicts with anim '" .. anim_id .. "'")
+                        end
+                    end
+                end
             end
         end
     end

manifest.lib

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