[R055LE]

Implements #47. Keep the issue open until the next signed owner-device candidate verifies the path.

What changed

• A saved host's primary Home action prepares a connection using its preferred identity. A saved password still goes through the system approval prompt.
• Missing credentials open a focused sign-in screen. Change identity and Edit are separate actions; a one-off identity choice does not update the saved preference.
• Validate an imported key at credential load so an encrypted key asks for its passphrase before SSH starts. Direct saved-host connections do not inherit unsaved editor history settings.
• Update the product spec and add Compose and key-store regressions, including 200% font scale and failed credential paths.

Validation

• ./gradlew test lint assembleDebug connectedDebugAndroidTest passed with the Android SDK configured.
• Android instrumentation: 124 tests, 119 passed, 5 skipped. Skips require the optional SSH fixture, performance opt-in, or an emulator device lock.
• The signed owner-device path remains for the next candidate, as requested by Connect a saved host directly from Home #47.