Refresh stale Android and WASM integration-test payloads

## Problem

Several active XHarness integration-test payloads are substantially older than the platforms on which they now run:

- `android/test-apk/x86/System.Buffers.Tests-x86.apk` was last updated in October 2020.
- `android/test-apk/x86_64/System.Buffers.Tests-x64.apk` was last updated in October 2020.
- `wasm/Common.Tests.zip` was last updated in May 2023.

Old prebuilt applications can stop installing or running as platform requirements advance, and their source revision and build settings are not evident from the blob name.

## Proposed work

- Rebuild the two Android `System.Buffers.Tests` payloads from a current supported runtime revision using supported Android SDK settings.
- Validate them on the Android API levels and architectures used by XHarness CI.
- Validate the WASM payload against the current browser/WASM integration-test environment and rebuild it if it no longer represents supported behavior.
- Upload refreshed artifacts under unambiguous architecture/version paths and update XHarness references.
- Record the source revision, build command, minimum platform level, and validation results for each refreshed payload.

## Completion criteria

- Active Android payloads install and pass on the current XHarness CI queues.
- The WASM payload has been validated and refreshed if necessary.
- Each payload has reproducible provenance and supported-platform metadata.

_This issue was created with AI assistance._

Start with the existing payloads at android/test-apk/x86/System.Buffers.Tests-x86.apk, android/test-apk/x86_64/System.Buffers.Tests-x64.apk, and wasm/Common.Tests.zip, then locate the XHarness references to them. Rebuild or validate each artifact using supported platform settings, test them on the stated CI environments, and record provenance, commands, minimum platform levels, and validation results.

Written by the indexing model from the issue text.