fix(deck): refine Moonlight preflight preview layout

[papi-ux]

Summary

• Refines the Steam Deck right-rail layout for the Moonlight handoff preflight preview.
• Adds a compact Review path card and reduces dense copy in the safe-launch/Moonlight panels.
• Keeps Moonlight preview copy gated by safe preflight/runtime state so blocked states do not imply an argv plan is usable.

Safety boundaries

• QML/layout-only polish.
• No Moonlight launch.
• No Sunshine launch.
• No Steam/game stream.
• No network discovery, pairing, credentials, host mutation, or HostStore persistence.
• No release/deploy/shortcut changes.

Test Plan

• pc-papi Qt Deck build
• pc-papi CTest suite
• Moonlight handoff source guard
• git diff --check
• SteamOS container build
• SteamOS container CTest suite
• Local 1280x800 render visual QA
• Real Steam Deck staged smoke/capture, no release-state changes

Notes

• Public PR intentionally omits private artifact paths and device connection details.
• Real-device evidence is retained in local handoff artifacts.