fix: GlitchTip source map upload flow; add AGENTS.md

Add 'releases new' and 'releases finalize' steps around sourcemaps
upload in release.yaml — without an explicit 'releases new' call,
GlitchTip creates the release entry but associates 0 files.

Add root AGENTS.md (picked up by Claude, Cursor, Copilot, etc.) with
full project context: stack, repo layout, Gitea CI conventions,
GlitchTip DSN/upload flow, infra, and iOS notes.

.gitea/workflows/release.yaml

@@ -172,6 +172,14 @@ jobs:
           SENTRY_ORG: libnovel
           SENTRY_PROJECT: ui
 
+      - name: Create GlitchTip release
+        run: glitchtip-cli releases new ${{ gitea.ref_name }}
+        env:
+          SENTRY_URL: https://errors.libnovel.cc/
+          SENTRY_AUTH_TOKEN: ${{ secrets.GLITCHTIP_AUTH_TOKEN }}
+          SENTRY_ORG: libnovel
+          SENTRY_PROJECT: ui
+
       - name: Upload source maps to GlitchTip
         run: glitchtip-cli sourcemaps upload ./build --release ${{ gitea.ref_name }}
         env:
@@ -180,6 +188,14 @@ jobs:
           SENTRY_ORG: libnovel
           SENTRY_PROJECT: ui
 
+      - name: Finalize GlitchTip release
+        run: glitchtip-cli releases finalize ${{ gitea.ref_name }}
+        env:
+          SENTRY_URL: https://errors.libnovel.cc/
+          SENTRY_AUTH_TOKEN: ${{ secrets.GLITCHTIP_AUTH_TOKEN }}
+          SENTRY_ORG: libnovel
+          SENTRY_PROJECT: ui
+
   # ── docker: ui ────────────────────────────────────────────────────────────────
   docker-ui:
     name: Docker / ui