Fix check-dts failure by removing .d.ts dependency on runtime interface.ts

[Copilot]

check-dts was failing because API Extractor traversed src/core/assets/@types/interface.ts from declaration files and raised ae-wrong-input-file-type, which then caused DTS generation to fail.
This change keeps the affected declaration files self-contained so API Extractor only processes declaration-safe inputs.

• Root-cause alignment

  • Removed .d.ts imports/re-exports that referenced ./interface.ts under src/core/assets/@types.

• Declaration-surface adjustments

  • In asset-types.d.ts, replaced derived runtime-based declarations with explicit declaration-time unions:
    • ISupportCreateType
    • AssetHandlerType
  • In userDatas.d.ts, inlined declaration enums used by types:
    • NormalImportSetting
    • TangentImportSetting
  • Removed export * from './interface' from userDatas.d.ts.

• Representative change

  // before (.d.ts pulled runtime .ts)
  import { NormalImportSetting, TangentImportSetting } from './interface';
  export * from './interface';
  
  // after (.d.ts is self-contained)
  export declare enum NormalImportSetting { optional = 0, exclude = 1, require = 2, recalculate = 3 }
  export declare enum TangentImportSetting { exclude = 0, optional = 1, require = 2, recalculate = 3 }