feat: activate verified MobileCore Omni runtime

[Harzva]

Summary

• add typed MobileCore Omni status and a dedicated verified-pair load route
• reject partial, unverified, path-like, or post-load digest-mismatched artifacts
• recheck the active libmtmd runtime and exact image/audio capability before media use
• add explicit control-sheet activation and safe reactivation for selected local attachments
• record redacted activation metadata in ActionEvidence without paths, payloads, or media
• document final Android emulator dual-app evidence and preserve physical-device/real-Omni gates

Verification

• 43 focused MobileCore client/adaptive-policy/approval tests passed
• 577 full Flutter tests passed
• pureDebug Android APK built as 0.1.77+67
• final APK SHA-256: 3833b98f95c113454658d471e9824bb66d2f83c9117c03c48d192a86a47a3c11
• final APK installed after removing the differently signed official QA copy; cold launch succeeded in 2694 ms
• MobileCore 0.1.4-rc4 loaded qwen2.5-0.5b by public ID and the real control sheet displayed the active model, runtime, quantization, preflight, metrics, installed models, and image/audio capability state
• filtered logcat contained no fatal exception, ANR, OOM, or SIGABRT marker
• Semgrep secrets scan: 0 findings

Open gates

• no physical Android device is connected
• the known iPhone 11 is unavailable
• this emulator lacks the verified Qwen2.5-Omni main/projector pair and fails its memory/storage preflight, so successful real Omni image/audio execution is not claimed
• the v0.1.77 background-service regression recorded on main-dev remains a separate MobileCore gate