docs: showcase themes on the host selection screen

[papi-ux]

Summary

• The theme cycler now flips through the host selection screen instead of the Stage view. The nav rail, filter chips, host cards, and status dots take each palette visibly, where the Stage view was dominated by game artwork. Five fresh Retroid Pocket 6 captures, one per theme, with the real host name and address pixelated in place before the resize, the same disclosed treatment as the live Mission Control still; derivation and raw sources recorded in the capture evidence manifest.
• The live gameplay still leaves the Control section. It showed neither NovaHUD nor the Command Center, so it read as game art rather than product proof. The Command Center capture continues to carry that section.

Verification

• bash scripts/check-public-docs.sh green; native submodule preflight and Retroid smoke unittests green.
• Referenced media total 321,098 bytes of the 1,000,000 cap; word count 1,408 of the 1,800 cap.
• New cycler verified by RIFF inspection: infinite loop, five frames at exactly 1800 ms, 92,532 bytes at 960x540.
• Device state restored after capture: Polaris Aurora theme reapplied and verified on screen.