fix(ci): revert to single task check step to preserve build cache

Splitting into separate steps breaks the Dart compilation cache that task
check builds up via parallelism. Without the shared cache, flutter test
integration_test/ -d linux rebuilds cold (9+ min instead of ~24s).

Keep the single 'nix develop --command task check' step which runs
analyze+build-linux+test in parallel (Task deps) and warms the cache
before the E2E test. Add timeout-minutes: 20 as a job-level safety net.
The xvfb-run timeout 600 (already in integration_ui_test.sh) still
prevents infinite hangs.

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

.forgejo/workflows/ci.yml

@@ -9,7 +9,7 @@ jobs:
   check:
     name: Full Project Check
     runs-on: self-hosted
-    timeout-minutes: 30
+    timeout-minutes: 20
 
     steps:
       - uses: actions/checkout@v4
@@ -19,27 +19,8 @@ jobs:
           mkdir -p ~/.config/nix
           echo "experimental-features = nix-command flakes" >> ~/.config/nix/nix.conf
 
-      - name: Generate changelog
-        run: nix develop --command task generate-changelog
-
-      - name: Analyze
-        run: nix develop --command task analyze
-
-      - name: Unit + Widget tests
-        run: nix develop --command task test
-
-      - name: Build Linux
-        run: nix develop --command task build-linux
-
-      - name: Integration tests
-        run: nix develop --command task integration
-
-      - name: UI E2E tests
-        timeout-minutes: 12
-        run: nix develop --command task integration-ui
-
-      - name: Coverage gate
-        run: nix develop --command task coverage
+      - name: Run Full Check Suite
+        run: nix develop --command task check
 
   build-linux:
     name: Build Linux Release