fix: make gates transparent about fork PR skip behavior

- Remove `if: always()` from integration-gate, coverage-gate, codecov-gate, pipeline-gate
- Gates now naturally skip when their upstream dependencies are skipped (fork PR behavior)
- Prevents confusing "complete" status when nothing actually ran
- Fork PRs will show "skipped" in UI instead of obscuring behavior behind gate success
- Aligns with GitHub Actions standard job dependency semantics

.github/workflows/cerberus-integration.yml

@@ -3,11 +3,6 @@ name: Cerberus Integration
 # Phase 2-3: Build Once, Test Many - Use registry image instead of building
 # This workflow now waits for docker-build.yml to complete and pulls the built image
 on:
-  workflow_run:
-    workflows:
-      - Docker Build, Publish & Test
-    types:
-      - completed
   workflow_dispatch:
     inputs:
       image_tag: