fix(android): reject invalid manifest XML before parsing

[OskarEichler]

Summary

XMLValidator.validate() returns either true or an error object. The previous truthiness check accepted the error object, so malformed manifests could be parsed as if validation succeeded. Require an actual true result.

The existing multi-activity fixture also contained an unmatched </queries> tag. This PR corrects that fixture and adds a dedicated malformed-manifest regression.

Compatibility

Malformed manifests now return null instead of occasionally yielding a launcher from partially parsed XML. Valid manifests retain their existing behavior. No dependency or SDK version changes.

Verification

• yarn build
• yarn test packages/cli-config-android/src/config/__tests__/getMainActivity.test.ts --runInBand (6 tests passed)
• Focused ESLint on the implementation and test
• Focused Prettier check on the TypeScript files
• git diff --check

Type: fix

[OskarEichler]

Resolved the draft blocker: I removed the stray unmatched </queries> from the shared multi-activity fixture and added an explicit malformed-manifest regression. The focused suite now passes all 6 tests, and the full package build plus focused lint/format checks are clean. I’ve marked the PR ready for review.