Add shell fixture script and verify production build tag

.gitignore

@@ -40,3 +40,7 @@ legacy/releases/
 __pycache__/
 plans/codex-shots*/
 plans/codex-report*.md
+
+# performance harness artifacts and temp files
+perf/fixtures/
+perf/.tmp/

perf/make-shell-fixture.sh

@@ -0,0 +1,126 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# ==============================================================================
+# perf/make-shell-fixture.sh
+# Archives frontend from <commit> into perf/fixtures/shell-<tag>/,
+# computes the build tag the way server.js computeBuildTag() does,
+# and verifies that it matches expected-tag (or live prod tag).
+# ==============================================================================
+
+if [ $# -lt 1 ]; then
+  echo "Usage: $0 <commit> [expected-tag]" >&2
+  exit 1
+fi
+
+COMMIT="$1"
+EXPECTED_TAG="${2:-}"
+
+REPO_ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+PERF_DIR="$REPO_ROOT/perf"
+FIXTURES_DIR="$PERF_DIR/fixtures"
+TMP_DIR="$PERF_DIR/.tmp"
+
+mkdir -p "$FIXTURES_DIR" "$TMP_DIR"
+
+PROD_URL="https://worship.hesed.sbs/api/version"
+
+fetch_prod_tag() {
+  curl -s -S --max-time 10 "$PROD_URL" | node -e '
+    let data = "";
+    process.stdin.on("data", chunk => { data += chunk; });
+    process.stdin.on("end", () => {
+      try {
+        const j = JSON.parse(data);
+        if (j.buildTag) {
+          process.stdout.write(j.buildTag);
+          process.exit(0);
+        }
+      } catch {}
+      process.exit(1);
+    });
+  ' 2>/dev/null || echo ""
+}
+
+# Verify the commit exists in git
+if ! git rev-parse --verify "$COMMIT^{commit}" >/dev/null 2>&1; then
+  echo "Error: commit '$COMMIT' not found in git repository" >&2
+  exit 1
+fi
+
+RESOLVED_COMMIT="$(git rev-parse --short=7 "$COMMIT")"
+echo "Extracting frontend from commit $RESOLVED_COMMIT..."
+
+STAGING_DIR="$(mktemp -d "$TMP_DIR/fixture-staging-XXXXXX")"
+cleanup() {
+  rm -rf "$STAGING_DIR"
+}
+trap cleanup EXIT
+
+# Archive frontend tree into staging dir
+git archive "$COMMIT" frontend | tar -x -C "$STAGING_DIR" --strip-components=1
+
+# Compute build tag using the exact logic from server/server.js computeBuildTag()
+COMPUTED_TAG=$(node -e '
+const { createHash } = require("crypto");
+const { readdirSync, statSync, readFileSync } = require("fs");
+
+function computeTag(dir) {
+  const hash = createHash("sha256");
+  const walk = (d, prefix) => {
+    for (const name of readdirSync(d).sort()) {
+      const full = `${d}/${name}`;
+      const rel = `${prefix}/${name}`;
+      if (statSync(full).isDirectory()) {
+        walk(full, rel);
+      } else {
+        hash.update(rel);
+        hash.update(readFileSync(full));
+      }
+    }
+  };
+  walk(dir, "./public");
+  return hash.digest("hex").slice(0, 12);
+}
+
+const tag = computeTag(process.argv[1]);
+process.stdout.write(tag);
+' "$STAGING_DIR")
+
+echo "Computed build tag for $RESOLVED_COMMIT: $COMPUTED_TAG"
+
+# Determine target expected tag
+if [ -z "$EXPECTED_TAG" ]; then
+  echo "Querying live production tag from $PROD_URL..."
+  EXPECTED_TAG="$(fetch_prod_tag)"
+  if [ -z "$EXPECTED_TAG" ]; then
+    echo "Error: failed to fetch live buildTag from $PROD_URL" >&2
+    exit 1
+  fi
+  echo "Live production build tag: $EXPECTED_TAG"
+
+  # If mismatch, deploy might be in progress: wait 5 minutes and retry once
+  if [ "$COMPUTED_TAG" != "$EXPECTED_TAG" ]; then
+    echo "Tag mismatch detected (computed=$COMPUTED_TAG vs prod=$EXPECTED_TAG)."
+    echo "Deploy may be in progress. Waiting 300 seconds to retry once..."
+    sleep 300
+    EXPECTED_TAG="$(fetch_prod_tag)"
+    echo "Retried production build tag: $EXPECTED_TAG"
+  fi
+fi
+
+if [ "$COMPUTED_TAG" != "$EXPECTED_TAG" ]; then
+  echo "Error: build tag mismatch! Computed '$COMPUTED_TAG' does not match expected '$EXPECTED_TAG'" >&2
+  exit 1
+fi
+
+TARGET_FIXTURE_DIR="$FIXTURES_DIR/shell-$COMPUTED_TAG"
+echo "Installing fixture into $TARGET_FIXTURE_DIR..."
+rm -rf "$TARGET_FIXTURE_DIR"
+mkdir -p "$TARGET_FIXTURE_DIR"
+cp -a "$STAGING_DIR"/. "$TARGET_FIXTURE_DIR"/
+
+FILE_COUNT=$(find "$TARGET_FIXTURE_DIR" -type f | wc -l)
+echo "Success: shell fixture created at $TARGET_FIXTURE_DIR with $FILE_COUNT files."
+echo "Verified commit: $RESOLVED_COMMIT"
+echo "Verified build tag: $COMPUTED_TAG"