fix: regenerate favicon.ico with a transparent ground; tick Pouya's read-through

public/favicon.ico shipped with no transparency: all three frames declared a
32-bit alpha channel and then carried alpha=255 on every one of their 256/1024/
2304 pixels, ground opaque cream rgba(250,247,242,255). Pouya's read-through
finding, confirmed by parsing the ICO container directly.

The render source carries true alpha (2,272,386 transparent px, 20,795 partial),
so this is an export, not a mask derived from the cream ground — R13's harder
branch did not fire and R13 is unchanged on its own terms.

New scripts/icons.mjs + npm run icons re-derives the icon from the committed
master: asserts the source is still the documented crop (R14), verifies a
candidate file and renames on success so a rejected build cannot replace a good
favicon, and runs a boundary-colour halo test. Composition is unchanged —
ink bbox and pixel count identical at all three sizes.

apple-touch-icon.png is byte-identical and stays opaque cream deliberately; the
reason lives in docs/reference/brand-assets.md §The icon set, with the bar and a
pointer in BaseLayout.astro, docs/06 and R13.

docs/06: the read-through is ticked, and the cutover callout drops to ONE
blocker — Q60's waiting period.

Two adversarial review rounds, 15 findings, all resolved, none declined; stopped
at two per D19. claims-auditor correctly deferred to cutover per D20. Gates on
the committed bytes, exit status read: check 0, build 0 (23 pages),
check:claims 0, check:intake 0, og:proof 0, lint 0, lighthouse 0 (worst of 23
99/100/100/100). Nothing deployed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Md3GndFqWPzK78xAoebsg5

src/layouts/BaseLayout.astro

@@ -56,7 +56,11 @@ const { preloadSerifItalic = false, ...seo } = Astro.props;
       /* No SVG favicon. The mark is a shaded ribbon, not flat vector paths, so
         there is no honest SVG of it to serve — see InfinityMark.astro and
         AGENTS.md Q38. The .ico carries 16/32/48, and is what crawlers request
-        at the root regardless of what is declared here. */
+        at the root regardless of what is declared here.
+
+        The .ico is transparent and the touch icon is opaque cream ON PURPOSE —
+        do not change either to match the other:
+        docs/reference/brand-assets.md §The icon set. */
     }
     <link rel="icon" href="/favicon.ico" sizes="16x16 32x32 48x48" />
     <link rel="apple-touch-icon" href="/apple-touch-icon.png" />