[ranjian0]

Closes #14

API

class Bone:
    name: str
    offset_matrix: tuple[tuple[float, ...], ...]   # 4x4 bind pose, like Node.transformation
    num_weights: int
    weights: memoryview            # float32, N
    weight_vertex_ids: memoryview  # uint32, N (parallel)
    armature_name: str | None      # populated only with Process_PopulateArmatureData
    node_name: str | None

class Animation:
    name: str
    duration: float                # in ticks
    ticks_per_second: float        # 0.0 = unspecified (duration is seconds)
    num_channels: int
    channels: list[NodeAnim]

class NodeAnim:
    node_name: str
    num_position_keys: int;  position_key_times: memoryview   # float64, N
                             position_key_values: memoryview  # float32, N*3
    num_rotation_keys: int;  rotation_key_times / rotation_key_values  # N*4 (x,y,z,w)
    num_scaling_keys: int;   scaling_key_times / scaling_key_values    # N*3
    pre_state: int                 # AnimBehaviour_* (before first key)
    post_state: int                # after last key

Mesh  += num_bones: int, bones: list[Bone]           # empty list when absent
Scene += num_animations: int, animations: list[Animation]

new constants: Process_PopulateArmatureData, AnimBehaviour_DEFAULT/_CONSTANT/_LINEAR/_REPEAT

Also included

• Memoryview lifetime fix: exported memoryviews (vertices, weights, keys, ...) are now backed by an internal buffer-keeper object, so data lives as long as any view references it. Previously buffers were freed with their owner while views could still exist (use-after-free; present since 1.1.0). Pinned by test_memoryviews_outlive_scene.
• scripts/memprof.py rewritten as an RSS leak harness (cyborg / planet / fox plain / fox skeletal / retained-memoryviews cases, allocator warmup + confirmation pass). All cases clean.
• examples/demo.py (pip install assimp-py[demo], make demo): pygame + moderngl demo — textured cyborg + GPU-skinned animated fox, animation evaluated in numpy from the new API (lerp/slerp keyframes, hierarchy walk, global(node) @ offset_matrix palette), orbit camera, HUD, skinned wireframe + skeleton overlays, --screenshot headless mode.
• Tests: tests/test_skeletal.py + fox fixture — bones (counts, names, offset matrices, parallel weight views, per-vertex weight sums), animations (3 Fox cycles with pinned durations/keys), armature/node names with and without the flag, empty-list behavior for static meshes. Fixture: Fox.glb from KhronosGroup/glTF-Sample-Assets (license included).
• README: skeletal animation usage + demo sections; .pyi stubs updated.

Out of scope (follow-ups)

Morph-target/mesh-swap animation channels (needs aiMesh::mAnimMeshes exposure), key-level interpolation data.