docs: compare three panel headers against the current one

At nav size the stamp cannot carry itself: its perforation is under a
pixel and its brick field dissolves into the brick bar, leaving a thin
frame around the name. The perforated edge under the bar was also drawn
inverted - round bumps with pointed gaps, where a real perforation is
round holes with flat teeth.

header/ puts the current header beside three replacements on a real
page: A, the wordmark alone with round holes of page colour bitten into
the bar at the mark's own hole-to-tooth ratio; B, the wordmark on a plain
bar; C, a stamp-paper header with an ink hairline, the mark's
perforation, and brick only behind the name. The wordmark files are the
stamp's own outlines, cut out of selfpost-stamp-compact.svg.

A comparison sheet pending the owner's choice; the 33 mockups and the
design contract are unchanged. Also tracks .claude/launch.json, the
local static server the mockups are previewed with.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

CHANGELOG.md

@@ -23,6 +23,16 @@ document is not part of the release.
 
 ### Added
 
+- Panel redesign, header comparison sheet
+  ([docs/assets/panel-redesign/header/](docs/assets/panel-redesign/header/index.html)):
+  at nav size the stamp dissolves into the brick bar and the perforated edge
+  was drawn inverted (round bumps instead of round holes). Three replacements
+  beside the current header — **A** wordmark with the stamp's real hole-to-tooth
+  perforation bitten into the bar, **B** wordmark on a plain bar, **C** a
+  stamp-paper header with an ink hairline and brick only behind the name. The
+  wordmark is cut from the stamp's own outlines. Pending the owner's choice;
+  the mockups are unchanged. `.claude/launch.json` serves the mockups locally
+  (`python -m http.server 8765` from the repository root).
 - Panel redesign, the roadmap's screens: **Inbound › Filter lists** and the
   adjusted **Inbound › Log** (client, decision, engine and reason; *Allow /
   Deny sender*) for inbound-antispam-panel, **Inbound › Quarantine** (list and