fix(rendering): align cross-platform output and harden pipeline

[JimmyDaddy]

Summary

• align iOS and Android geometry, rotation, transparency, text defaults, and watermark orientation behavior
• harden image loading, validation, output paths, atomic writes, concurrency, cancellation, and bitmap ownership
• preserve legacy JavaScript API compatibility while adding native unit, instrumentation, and real JS-to-native E2E coverage
• add an Expo clean-install bundle smoke check and archive the completed follow-up review

Root cause

The native rendering pipelines had diverged in coordinate scaling, defaults, orientation handling, URI decoding, and output persistence. Invalid parameters and unsafe file names were not rejected consistently, while concurrent jobs could retain large image resources longer than necessary. Existing coverage did not exercise enough public bridge and platform-specific behavior to catch these regressions.

Impact

• makes rendering behavior more consistent across iOS and Android
• restores expected transparent text/background output and watermark orientation
• supports sampled content/resource URI and Base64 JPEG loading on Android
• rejects invalid quality, alpha, size, and output file names before unsafe native work
• bounds concurrent image work, improves cancellation cleanup, and avoids partial output files
• keeps legacy watermarkImage callers working

Validation

• ESLint
• Jest: 13/13
• root, API fixture, example, and Expo TypeScript checks
• Android unit tests: 52/52
• Android loader instrumentation: 8/8
• Android renderer instrumentation: 17/17
• Android public JS-to-native E2E: 2/2
• iOS CI test whitelist: 27/27
• Android release assemble and iOS simulator Release build
• package prepack, generated docs, Expo Android export smoke
• actionlint for the changed CI workflow and git diff checks

Closes #297
Closes #298