fix(android): close hash and random-access files before settling

[OskarEichler]

Fixes

Close hash/read and random-access write handles before promise completion. Preserve the original error when closing also fails, and avoid double-close paths. Replace a per-call six-entry hash-algorithm map and per-byte String.format with direct dispatch and hexadecimal character lookup. Accept extensionless raw-resource names; preserve existing extension-based routing and document it.

Compatibility / observable changes

No public signatures, algorithms or digest output change. Close failures now reject instead of resolving first or escaping after settlement. Extensionless names resolve through res/raw rather than throwing a substring-index error.

Verification

Actual Kotlin method bodies with real temporary file data and instrumented I/O constructors: all six digest algorithms at 0, 1, 255 and 20,000 bytes match Java MessageDigest/HexFormat; append/random-access writes cover success, write failure, close failure and combined errors. Thirty of 33 baseline lifetime/error checks fail; all 33 fixed cases pass. Four actual resource-name mapping cases pass (one baseline failure). Fewer formatting/map allocations follow directly from the code change; no app-wide speedup is claimed.

Shared checks and limits

Combined upstream lint/TypeScript and whitespace checks pass. Full Android Kotlin compilation against RN 0.87.1 and all six Apple implementation compilations against the iOS Simulator SDK pass. No checked-in tests/specs changed; diagnostic harnesses live outside the repository. Simulated/native-API-double checks are not physical-device verification. Consumer pin 99772cc: immutable install/lint, both Android Debug flavors and both iOS Simulator schemes pass. All 72 installed non-metadata files match reviewed source/build artifacts. JS/declarations are unchanged from the preceding verified pin, which passed four Metro bundles, 13 web builds and four extensions. Windows runtime and physical devices remain unverified.