fix(input): surface service-mode control limits

[bestlux]

Summary

• add an authenticated layout matrix transport payload so explicit layout applies sync/mirror to connected trusted peers
• report Windows service/session-0 input as unsupported instead of showing an active capture target that cannot control the interactive desktop
• fail incoming service-session input injection with a stable diagnostic reason

Root cause

Dogfood showed connected peers could queue synthetic input frames, but LocalSystem service-mode capture/injection did not affect the interactive desktop. The previous status path still surfaced active-looking input state, so the tray could show a green/armed control path that was not actually usable.

Validation

• cargo fmt --all -- --check
• cargo test -p core-protocol wire_message_layout_matrix_round_trip
• cargo test -p boundless-daemon local_layout_update_queues_sync_for_connected_peer
• cargo test -p boundless-daemon incoming_layout_matrix_is_mirrored_to_local_view_without_rebroadcast
• cargo test -p boundless-daemon flush_sends_layout_matrix_payload
• cargo test -p boundless-daemon service_session
• git diff --check
• cargo clippy --workspace --all-targets -- -D warnings
• cargo test -p boundless-daemon --lib
• cargo test --workspace --quiet

Notes

• Actual mouse/keyboard control from the MSI-owned service remains deferred to a user-session input broker/helper.
• This PR intentionally does not change installer, firewall, reset, trust, or pairing behavior.