[SashaRX]

Problem and change

A collision node such as Seat_COL with its own M_Wood_Oak material and no matching render sibling received no surface binding. The Colliders step only inspected render siblings, and Apply removed the collision renderer before resolving its surface.

Read surface evidence before renderer removal and inspect the node's own materials before matched render siblings. Explicit surface words in the part name still take priority. No game types, assembly dependencies, serialized settings or binding interfaces are added.

Verification

• Added 9 EditMode test cases for own-material Preview/Apply parity (root and non-root placement), name/material/fallback precedence, preservation of an existing different reference, missing-asset retry on a non-root collider, incompatible data types, and real AssetDatabase lookup with prefab-variant reload.
• Extended the resolver test to document first-recognized-material behavior.
• Both compile-check FBX variants compile against Unity reference assemblies: 0 warnings, 0 errors. Used single-node MSBuild with build servers disabled due to the execution environment.
• Identifier check: 0 findings; tool dependency check: 0 violations; metadata and whitespace checks passed.
• Unity Editor is unavailable here, so EditMode tests have been added and compiled but not executed. This PR remains a draft pending Unity execution.

Integration boundaries

Documentation~/PREPARE_SURFACE_BINDING.md documents the existing API and limits: a root MeshCollider skips the entire Colliders step, mixed-material nodes receive one surface, a manual binding on a source node is not migrated when its collider moves to root, and missing assets are warnings. These policies are unchanged; this change does not claim to make existing-model migration or per-submesh ballistics complete.

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