Replace this draw's entire geometry in a single call: vertices, indices, and all extras channels.
Atomic: all fields update together, so cross-field length invariants are guaranteed. Prefer
this over per-slice setters when resizing the entire mesh.
Validation: every non-empty extras slice in must have length equal to
mesh.vertices.Length, AND its channel must be enabled on the panel's
ExtraVertexChannels mask. mesh.indices.Length must be a multiple of 3. If any
check fails the call is rejected (this draw stays unchanged) and an error is logged.
Metadata (renderType, phase, texture, userData) is preserved.