fix(presentation): handle force-push, branch-create, empty pushes

PushEvent payloads carry `created`, `forced`, `distinct_size`, and
`ref` flags that I wasn't consulting — the result on the timeline
was "pushed 0 commits" for what were actually branch creations
(distinct_size 0 because the commits already existed elsewhere)
and force-pushes that didn't change the resulting tree.

  * created=true        → "created branch X in repo" + GitBranchCreate icon
  * forced + size>0     → "force-pushed N commits to repo:branch"
  * forced + size==0    → "force-pushed repo:branch"
  * normal + size>0     → "pushed N commits to repo:branch" (unchanged)
  * normal + size==0    → "pushed to repo:branch" (no awkward "0 commits")

Also: drop the instagram, facebook, and steel-horse-adventures
links from the UI header — those represent personae the user no
longer wants to surface from rob.tn.

Tests: +3 in presentation/github.rs covering the new push
branches — 21 total green.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

ui/src/App.tsx

@@ -18,13 +18,10 @@ const RANGE_MIN = new Date('2010-01-01T00:00:00Z').getTime();
 const RANGE_MAX = Date.now();
 
 const externalLinks: { url: string; alt: string }[] = [
-  { url: 'https://instagram.com/rob_thij', alt: 'instagram' },
-  { url: 'https://www.facebook.com/rob.thijssen', alt: 'facebook' },
   { url: 'https://linkedin.com/in/thijssen/', alt: 'linkedin' },
   { url: 'https://stackoverflow.com/users/68115/grenade', alt: 'stackoverflow' },
   { url: 'https://github.com/grenade', alt: 'github' },
   { url: 'https://git.lair.cafe/grenade', alt: 'gitea' },
-  { url: 'https://steelhorseadventures.com', alt: 'steel horse adventures' },
 ];
 
 export default function App() {