ci: self-updating README banner + fix webpage count sync (#119)

* ci: fix webpage count sync crashing on removed public/hero.svg

The webpage indicator-count sync sed'd index.md, .vitepress/config.ts and
public/hero.svg, but hero.svg was removed from wickra-lib/webpage (the count is
now baked into og-banner.webp at build time from index.md). Under 'bash -e' the
missing file made sed exit 2 before the commit/push, so the count never reached
the webpage repo and its OG banner stayed stale — masked green by the step's
continue-on-error. Drops public/hero.svg from the sed and git add; index.md and
.vitepress/config.ts (both still carry the count) remain.

* docs: point README banner at the self-updating org profile image

Switches the top README banner from https://wickra.org/og-banner.webp (baked at
webpage deploy time) to the org profile banner that wickra-lib/.github's
banner.yml regenerates from the indicator count on every sync
(raw.githubusercontent.com/wickra-lib/.github/main/profile/wickra-banner.webp).
The ?v=227 query busts GitHub's Camo image cache; the next commit teaches
sync-about to bump it with the count.

* ci: bump README banner cache-buster alongside the indicator count

Extends the PR-head README counter patch to also rewrite wickra-banner.webp?v=N
to the current count. The banner now points at the org profile image, whose
content changes when .github/banner.yml regenerates it; bumping the ?v query
busts GitHub's Camo cache so the README shows the new banner immediately. Rides
in the existing count-sync commit, so no extra commit lands on main.

* docs: changelog entry for self-updating README banner and sync fix

CHANGELOG.md

@@ -43,6 +43,14 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   every candlestick pattern, making the family a drop-in machine-learning
   feature where bullish and bearish instances share a single dimension.
 
+### Fixed
+- **README banner now self-updates.** The top README banner points at the org
+  profile image that `.github/banner.yml` regenerates from the indicator count,
+  and `sync-about.yml` bumps a `?v=<count>` cache-buster so GitHub's Camo proxy
+  refetches it immediately. Also fixes the webpage indicator-count sync, which
+  silently crashed on a removed `public/hero.svg` and left the marketing site's
+  count (and its OG banner) stale.
+
 ### Security
 - **CI dependency installs are pinned by hash.** The Node binding now installs
   with `npm ci` (strict `package-lock.json`), and the Python CI/bench tooling is