fix(poll): match run path with @ref suffix in in-flight guard

Gitea's runs API returns path as "build-prerelease.yml@refs/heads/main",
so endswith(".yml") never matched and the guard counted 0 with a build
demonstrably in flight (run 3230 was cancelled by the test dispatch).
Match on startswith("<file>@") instead, with a null-guard for runs
lacking the field. Verified against the live API: counts the in-flight
run correctly.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.gitea/workflows/poll-upstream.yml

@@ -78,7 +78,8 @@ jobs:
       # executing would cancel it (concurrency cancel-in-progress) and restart
       # identical work — builds longer than the poll interval could never
       # finish. Skip dispatching and let the running build complete; the next
-      # poll re-checks the published RPMs.
+      # poll re-checks the published RPMs. Note: the runs API reports path as
+      # "<file>@<ref>", hence the startswith match.
       - name: Check for in-flight release build
         id: inflight
         run: |
@@ -86,7 +87,7 @@ jobs:
             --header "Authorization: token ${{ secrets.DISPATCH_TOKEN }}" \
             --url "${{ github.server_url }}/api/v1/repos/${{ github.repository }}/actions/runs?limit=50" \
             | jq '[.workflow_runs[]
-                   | select(.path | endswith("build-release.yml"))
+                   | select((.path // "") | startswith("build-release.yml@"))
                    | select(.status != "completed")] | length')
           echo "count=${count}" >> "$GITHUB_OUTPUT"
           echo "in-flight build-release runs: ${count}"
@@ -170,7 +171,7 @@ jobs:
             --header "Authorization: token ${{ secrets.DISPATCH_TOKEN }}" \
             --url "${{ github.server_url }}/api/v1/repos/${{ github.repository }}/actions/runs?limit=50" \
             | jq '[.workflow_runs[]
-                   | select(.path | endswith("build-prerelease.yml"))
+                   | select((.path // "") | startswith("build-prerelease.yml@"))
                    | select(.status != "completed")] | length')
           echo "count=${count}" >> "$GITHUB_OUTPUT"
           echo "in-flight build-prerelease runs: ${count}"