fix(mobile): prevent text leaking through Android glass - #10998

Eligibility
This is a narrowly scoped mobile rendering fix that consolidates existing glass behavior and prevents Android background text from showing through translucent surfaces. Existing iOS native glass, non-blur fallbacks, and menu interactions remain intact, with no schema, deployment, security, or static-analysis changes.

Notes:
No code owners found in target merge base 75e4ceb