Post-v0.5.0 docs: Pages markdown fix, credit line, release-notes template, ROADMAP/D572

- Pages: the two cblock sections render as markdown under GitHub Pages'
  kramdown (markdown="1"); the Download block's unparsed `<file>` had swallowed
  every heading below it. Gallery alt text says 3840x2160.
- Credit line (README "How it was made" + social preview card): several coding
  agents directed by one maintainer, with a handful of contributors; card
  findings count 430.
- Release-notes template: drop the stale header-stills comment and the Aztec
  re-check-owed note.
- ROADMAP: Windows display-scaling (not DPI-aware) item
  D572: CI-tarball verification (glibc floor, X220 + Deck fresh
  install, 21/21 pixel gate on both).

docs/dev/findings.md

@@ -18410,3 +18410,10 @@ no longer serves `python3-pip`, so pip comes from a hash-pinned `get-pip.py`
 SDL `GLIBC_2.4`, `ge007-convert` built against 2.31. Verified: the container
 build run by hand on the X220 (podman) — fresh install there (ROM only ->
 converter -> boot -> clean quit, exit 0). No source changes; packaging only.
+
+CI-built tarball (run 37623073542, c45dece7, the v0.5.0 packaging): floor
+`GLIBC_2.29`, bundled SDL identifies as `SDL-release-2.30.0`. Fresh install
+(empty folder + ROM -> converter -> boot -> clean quit, exit 0) passed on the
+X220 (Fedora 37, glibc 2.36: the box the 24.04 tarball refused to start on) and
+the Steam Deck; the 21-level pixel gate ran on that binary on both, 21/21 PASS
+each. Shipped in v0.5.0.