Docs: README + Pages landing overhaul for v0.2.0; Deck settings docs.

- README: manual Contents TOC dropped (GitHub auto-generates); Download
  table moved to the top with Quick start under it; Status compressed to
  a Working paragraph + tight known-issue list (D-numbers live in the
  release notes / finding log now); How-it-works tightened.
- Pages (docs/index.md): demo gif is the hero; download table up top;
  new How-it-works and Honest-status sections; legal footer; the 19-shot
  playtest gallery unchanged.
- Options overlay is now gamepad-driven: README Steam Deck section, the
  bundle README (new @DECK@ block on Linux, controller column added to
  the controls table), and the release-notes template all document
  Select / D-pad / A / B / Start instead of a Steam key-mapping workaround.

.github/release-notes.md

@@ -82,6 +82,11 @@ region from the SHA-1. US is the best-tested.
 **Steam Deck:** sideload the unpacked folder (USB or a file manager), do steps
 2–4, then add the executable to Games → *Add Game* as a non-Steam game.
 
+**In-game settings on the Deck:** the options overlay is fully gamepad-driven
+— it opens with **Select**, the D-pad or left stick (up/down) moves between
+options, **A** steps the selected option forward, **B** steps it back, and
+**Start** (or Select again) closes. No keyboard needed.
+
 Full steps are in the bundled `README.md`.
 
 ### Verify the download