CI: also build on push to main (code changes), keep cron for new releases

- push to main triggers a rebuild of the current version so build changes get
  tested; scoped to main so the job's pages/tag pushes can't loop it, and
  docs-only paths are ignored to avoid wasteful full rebuilds.
- the decide step treats a push (like a manual force) as build=true even when
  the version tag already exists.
- cron still handles new upstream binary releases as before.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.gitea/workflows/build-flatpak.yml

@@ -1,8 +1,22 @@
 name: Build and Publish O3DE Flatpak
 
 on:
+  # New O3DE binary release: the daily check rebuilds when upstream's version has
+  # no matching vX.Y.Z tag yet.
   schedule:
-    - cron: '0 2 * * *'          # daily at 02:00 - checks for a new O3DE release
+    - cron: '0 2 * * *'          # daily at 02:00
+  # Code change: rebuild whenever the build itself changes. Scoped to `main` on
+  # purpose - the job force-pushes the `pages` branch and creates tags, and those
+  # must NOT re-trigger it (that would loop). Docs-only changes are ignored so a
+  # README/typo edit doesn't kick off a ~15-min, multi-GB build.
+  push:
+    branches:
+      - main
+    paths-ignore:
+      - 'README.md'
+      - 'docs/**'
+      - 'LICENSE*'
+      - '.gitignore'
   workflow_dispatch:
     inputs:
       force:
@@ -61,9 +75,11 @@ jobs:
         id: check
         run: |
           git config --global --add safe.directory "$GITHUB_WORKSPACE"
-          if [ "${{ inputs.force }}" = "true" ]; then
+          # A code push (or a manual force) rebuilds even if this version is already
+          # published - the point is to test the changed build against it.
+          if [ "${{ inputs.force }}" = "true" ] || [ "${{ github.event_name }}" = "push" ]; then
             echo "build=true" >> "$GITHUB_OUTPUT"
-            echo "Force build requested."
+            echo "Rebuild requested (${{ github.event_name }})."
           elif git ls-remote --tags origin "refs/tags/v${{ steps.ver.outputs.version }}" | grep -q .; then
             echo "build=false" >> "$GITHUB_OUTPUT"
             echo "v${{ steps.ver.outputs.version }} already published - nothing to do."