ci: drop main-branch trigger so merge commits don't re-run dev CI

Mirrors the same fix applied to the fabledassistant repo: merges to
main only happen after dev already passed CI and tagged releases are
the sole trigger for a signed APK build, so re-running analyze+test on
the merge commit just burns runner time.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.forgejo/workflows/ci.yml

@@ -1,7 +1,12 @@
 # CI runs first; build only proceeds if all checks pass.
 #
-# Push to dev or main:  flutter analyze + flutter test
+# Push to dev:       flutter analyze + flutter test
-# Tag v* (release):     gates + signed APK build + attach to Forgejo Release
+# Tag v* (release):  gates + signed APK build + attach to Forgejo Release
+#
+# main pushes are NOT gated here: a merge to main only happens after
+# dev has already passed CI, and the release tag is the sole trigger
+# for a signed APK build. Re-running analyze+test on the merge commit
+# just burns runner time without changing the outcome.
 #
 # To cut a release:
 #   Create a release via the Forgejo UI on main with a v* tag name.
@@ -20,7 +25,7 @@ name: CI & Build
 
 on:
   push:
-    branches: [dev, main]
+    branches: [dev]
     tags: ["v*"]
 
 # Cancel older runs on the same branch when a newer push lands. Tag runs
@@ -63,7 +68,7 @@ jobs:
   build:
     name: Build release APK
     needs: [analyze]
-    # Only tag pushes produce a signed release build. dev/main pushes
+    # Only tag pushes produce a signed release build. dev pushes
     # run the gates above and stop there.
     if: startsWith(github.ref, 'refs/tags/')
     runs-on: ci-runner