UX: shared game settings and reversible settings trials #16

Scope

Replace separate everyday settings flows with shared Display / Controls pages in the library and in-game menu. Keep virtual phone resolution and compatibility options under Advanced. This is a general workflow improvement, not individual-game patches.

Acceptance

• Detached per-game draft; graphical mapper edits the same draft.
• Try, Keep and Undo; timeout rollback; no preview autosave over the confirmed profile.
• One-shot library trial, so a failed launch cannot replay it on next launch.
• First-launch preparation is retained when opening settings.
• Public Phone passes 66 selected Android tests; Handheld passes 10 new settings-trial tests; both JVM suites pass 14 tests.
• Finish emulator UI acceptance and commit the implementation (5a4bc72).

The legacy layout editor and ordinary edits in the full expert editor still save directly. Renderer/property rollback may require restarting the game. Physical-controller and external-launcher acceptance stay separate in #9 and #7.