fix: preserve File-like metadata in toFile

[pragnyanramtha]

Summary

• preserve type and lastModified when toFile() receives non-native File-like objects
• keep the native File fast path when no name/options override is requested
• copy native File values when callers provide explicit metadata overrides
• add upload helper coverage for preserving and overriding File-like metadata

Context

isFileLike() requires name, type, lastModified, and file methods, but toFile() rebuilt non-native File-like objects with only arrayBuffer() and name. That discarded useful upload metadata even though the input already exposed it.

Validation

• ./node_modules/.bin/jest tests/uploads.test.ts --runInBand -> 11 passed, 3 snapshots passed
• ./node_modules/.bin/prettier --check src/internal/to-file.ts tests/uploads.test.ts -> passed
• ./node_modules/.bin/eslint src/internal/to-file.ts tests/uploads.test.ts -> passed
• ./scripts/build -> passed
• git diff --check -> passed

I also tried yarn lint; it progressed through Prettier, ESLint, and build, then failed in repo-wide typecheck because this checkout is missing existing example dependencies (@azure/identity, express, and next). The touched implementation and upload tests pass their focused checks.

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