fix(test): stabilize CipherBoard 0.4.2 release gate - #28

Summary

• wait for the protected clipboard Activity to receive window focus before exercising Android foreground-only clipboard reads
• make the upstream timestamp test account for second-resolution formatting across a clock boundary
• prepare the v0.4.2 maintenance release without changing runtime cryptography, identities, sessions, or message formats

User-visible fixes included

• switch Russian/English layouts inside the embedded Private panel
• restore Private mode after switching to another Android keyboard and returning to CipherBoard
• retain explicit password-field warning while supporting ordinary text, numeric, multiline, and TYPE_NULL editors with a live InputConnection

Verification

• ./gradlew test :app:lintDebug :app:lintRelease :crypto-core:lintRelease :pairing:lintRelease :secure-storage:lintRelease :app:assembleDebug :app:assembleRelease --no-daemon (548 tasks)
• API 36 connected tests: crypto-core 1/1, app 7/7
• clipboard fallback focused instrumentation: 5 consecutive passes
• python scripts/security_source_scan.py .
• python scripts/kotlin_style_check.py .
• release tooling tests: 28/28
• git diff --check

Security scope

The runtime clipboard path is unchanged. The IME compatibility behavior remains bound to the exact current InputConnection, host identity, and editor metadata before ciphertext handoff.