ci(workflows): streamline CI and remove redundant builds (#31)

Streamline the CI and release workflows:

- ci.yaml is now PR-only (no push-to-main re-run) and keeps only lint and
  dependency-review; the gateway-image local build/smoke job is removed.
- Split the path-sensitive jobs into ci-python.yaml and ci-manifests.yaml,
  each using native on.pull_request.paths filtering so unrelated PRs skip them.
- Drop the duplicate check-manifests.py run from the lint job.
- release.yaml: skip the tests job steps for tags already on main (where PR CI
  already ran), keeping them only for release-branch tags.

Co-authored-by: SREDevOpsAgents <agents@sredevops.org>

.github/workflows/ci-python.yaml

@@ -0,0 +1,72 @@
+# Gateway unit tests and lint. Split from ci.yaml so this job can use native
+# on.pull_request.paths filtering and skip PRs that do not touch the gateway.
+# The job name is the required branch-protection check `python`.
+name: CI (python)
+
+on:
+  pull_request:
+    paths:
+      - examples/dsh-agents-as-a-service/gateway/**
+      - .github/workflows/ci-python.yaml
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+concurrency:
+  group: ci-python-${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  python:
+    name: python
+    runs-on: ubuntu-latest
+    timeout-minutes: 20
+    defaults:
+      run:
+        working-directory: examples/dsh-agents-as-a-service/gateway
+    steps:
+      - name: Checkout
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+      - name: Set up Python
+        uses: actions/setup-python@6d4fd22b20465ccc0f7354476588e8df7c9ca0e0 # v7.1.0
+        with:
+          python-version: "3.12"
+          cache: pip
+          cache-dependency-path: |
+            examples/dsh-agents-as-a-service/gateway/requirements.txt
+            examples/dsh-agents-as-a-service/gateway/requirements-dev.txt
+      - name: Install dependencies
+        run: |
+          set -euo pipefail
+          python -m pip install --upgrade pip
+          pip install -r requirements.txt -r requirements-dev.txt
+      - name: Lint
+        run: |
+          set -euo pipefail
+          python -m ruff check .
+          python -m ruff format --check .
+      - name: Unit tests with coverage
+        run: >-
+          python -m pytest -q
+          --cov=. --cov-report=xml:coverage.xml --cov-report=term
+          --junitxml=junit.xml
+      - name: Coverage summary
+        run: |
+          set -euo pipefail
+          {
+            echo "### Gateway test coverage"
+            python -m coverage report
+          } >> "$GITHUB_STEP_SUMMARY"
+      - name: Upload test artefacts
+        if: always()
+        uses: actions/upload-artifact@cf430e030ddbb5b0abf93d22962f4752f3646cd9 # v7.0.2
+        with:
+          name: gateway-test-results
+          path: |
+            examples/dsh-agents-as-a-service/gateway/junit.xml
+            examples/dsh-agents-as-a-service/gateway/coverage.xml
+          if-no-files-found: warn
+          retention-days: 7