fix(ci): smoke test hung 14min — buildah run doesn't die under plain timeout

Bare `/tapir` runs the long-running server, same as the old ctr-based smoke
test. ctr's --rm reliably force-killed it; a plain `timeout N buildah run`
does not — it only signals the wrapper, and the container process can
survive that and keep the log pipe open, hanging the whole job (observed
live: run 155, 14min before failure). Backgrounds the run and tears it down
with `buildah rm -f`, which forcibly kills regardless of wrapper state, and
captures output via a file instead of a blocking pipe.

Refs infra#132.

.gitea/workflows/ci.yml

@@ -82,13 +82,28 @@ jobs:
       # avoids sudo/host-containerd access so this still works once the
       # runner itself is containerized (infra#132). Tests the local
       # buildah-store image directly, no registry round-trip needed.
+      #
+      # Bare `/tapir` (no subcommand) runs the long-running server, same as
+      # the old ctr-based smoke test -- ctr's --rm reliably force-killed it,
+      # but a plain `timeout N buildah run` does NOT: it only signals the
+      # `buildah run` wrapper, and the actual container process can survive
+      # that and keep the output pipe open, hanging the whole job (hit this
+      # live: 14min hang, infra#132). Backgrounding the run + `buildah rm -f`
+      # decouples "is the script blocked" from "did the process exit" --
+      # rm -f forcibly tears down the container regardless of wrapper state.
       - name: Smoke test
         run: |
           REGISTRY="localhost:5000"
           REF="${REGISTRY}/${{ env.IMAGE }}:${{ steps.meta.outputs.sha-tag }}"
           CONTAINER=$(buildah from ${REF})
-          OUTPUT=$(timeout 5 buildah run "$CONTAINER" -- /tapir 2>&1 || true)
-          buildah rm "$CONTAINER" >/dev/null
+          LOG=$(mktemp)
+          buildah run "$CONTAINER" -- /tapir > "$LOG" 2>&1 &
+          RUNPID=$!
+          sleep 5
+          kill -9 "$RUNPID" 2>/dev/null || true
+          wait "$RUNPID" 2>/dev/null || true
+          buildah rm -f "$CONTAINER" >/dev/null 2>&1 || true
+          OUTPUT=$(cat "$LOG"); rm -f "$LOG"
           echo "$OUTPUT" | grep -q "tapir" \
             && echo "Smoke test passed" \
             || echo "Smoke test inconclusive: $OUTPUT"