fix(ci): cascade wait-step SHA capture leaked pip stdout (4th defect)

Run 5196 (2026-05-11 02:46Z, first-ever successful publish) succeeded
the publish job but failed the cascade job at the wait-for-PyPI-
propagation step:

  ::error::PyPI propagated 0.1.130 but wheel content SHA256 mismatch.
  ::error::Expected: 536b123816f3c7fb54690b80be482b28cabd1874690e9e93d8586af3864c7fba
  ::error::Got:      Collecting molecule-ai-workspace-runtime==0.1.130
  ::error::Fastly may be serving stale content. Refusing to fan out cascade.

The 'Got:' is pip's own stdout, not a SHA. Root cause:

  HASH=$(python -m pip download ... 2>/dev/null && sha256sum ... | awk ...)

The shell pipeline captures BOTH commands' stdout into $HASH. `2>/dev/null`
only silences stderr, not stdout. pip download writes 'Collecting ...' to
stdout by default, so it leaks into HASH ahead of sha256sum's output.

Fix: split into two steps, redirect pip stdout to /dev/null explicitly,
capture only sha256sum's output into HASH.

Impact: cascade-to-8-template-repos failed, but PyPI publish itself
succeeded. Users (workspace-template-* maintainers) can pin manually
via 'docker build --build-arg RUNTIME_VERSION=X.Y.Z' until cascade is
healed. hongming-pc is doing exactly this for the plugins_registry rollout.

4th and likely last workflow defect after #353, #355, #357.

Refs: #351, #353, #355, #357, #348 Q3

.gitea/workflows/publish-runtime.yml

@@ -207,13 +207,23 @@ jobs:
 
           # Stage (b): download wheel + SHA256 compare against what we built.
           # Catches Fastly stale-content serving old bytes under a new version URL.
-          HASH=$(python -m pip download \
-                    --no-deps \
-                    --no-cache-dir \
-                    --dest /tmp/wheel-probe \
-                    "molecule-ai-workspace-runtime==${RUNTIME_VERSION}" \
-                    2>/dev/null \
-                 && sha256sum /tmp/wheel-probe/*.whl | awk '{print $1}')
+          #
+          # Caught run 5196 (first-ever successful publish, 2026-05-11): the
+          # previous one-liner `HASH=$(pip download ... && sha256sum ...)`
+          # captured pip's stdout (`Collecting molecule-ai-workspace-runtime
+          # ==X.Y.Z`) into HASH, then the SHA comparison failed against the
+          # leaked `Collecting...` string. `2>/dev/null` silences stderr but
+          # NOT stdout; pip writes its progress to stdout by default.
+          # Fix: split into two steps, silence pip's stdout explicitly, capture
+          # only sha256sum's output into HASH.
+          python -m pip download \
+            --no-deps \
+            --no-cache-dir \
+            --dest /tmp/wheel-probe \
+            --quiet \
+            "molecule-ai-workspace-runtime==${RUNTIME_VERSION}" \
+            >/dev/null 2>&1
+          HASH=$(sha256sum /tmp/wheel-probe/*.whl | awk '{print $1}')
           if [ "$HASH" != "$EXPECTED_SHA256" ]; then
             echo "::error::PyPI propagated $RUNTIME_VERSION but wheel content SHA256 mismatch."
             echo "::error::Expected: $EXPECTED_SHA256"