ci: split into fast analyze + slow release build with path gating

analyze job runs on push/PR regardless of changed files (fast check).
release-apk job only fires when Dart source, Android, pubspec, or
tooling files change on push to master (slow build).
workflow_dispatch triggers both jobs unconditionally.
Doc-only pushes no longer trigger any CI run.

.github/workflows/ci.yaml

@@ -3,6 +3,13 @@ name: CI
 on:
   push:
     branches: [ master ]
+    paths:
+      - 'lib/**.dart'
+      - 'test/**.dart'
+      - 'android/**'
+      - 'tool/**'
+      - 'pubspec.yaml'
+      - 'pubspec.lock'
   pull_request:
     branches: [ master ]
   workflow_dispatch:
@@ -15,7 +22,7 @@ on:
 
 jobs:
   analyze:
-    name: Analyze & Build
+    name: Analyze & Test
     runs-on: flutter-android
     steps:
       - uses: actions/checkout@v4
@@ -31,6 +38,16 @@ jobs:
       - name: Analyze
         run: flutter analyze
 
+  release-apk:
+    name: Release APK
+    runs-on: flutter-android
+    needs: [analyze]
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Get dependencies
+        run: flutter pub get
+
       - name: Build release APK
         run: flutter build apk --release