Fall back to non-frozen pnpm install for control dir

The frozen lockfile install can fail when the control branch's lockfile
was generated with different pnpm settings. Fall back gracefully since
exact reproducibility of the control's node_modules is less critical
than being able to run the benchmark at all.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

Author: NullVoxPopuli

scripts/bench-compare.mjs

@@ -88,10 +88,18 @@ try {
 
   // ── 2. Install dependencies in control dir ───────────────────────────────
   console.error(`\n📦  Installing dependencies for control (${BASE_BRANCH})…\n`);
-  run('pnpm install --frozen-lockfile', {
-    cwd: CONTROL_DIR,
-    stdio: ['inherit', 'pipe', 'inherit'],
-  });
+  try {
+    run('pnpm install --frozen-lockfile', {
+      cwd: CONTROL_DIR,
+      stdio: ['inherit', 'pipe', 'inherit'],
+    });
+  } catch {
+    console.error('⚠️  Frozen install failed, retrying without --frozen-lockfile…\n');
+    run('pnpm install --no-frozen-lockfile', {
+      cwd: CONTROL_DIR,
+      stdio: ['inherit', 'pipe', 'inherit'],
+    });
+  }
 
   // ── 3. Run mitata bench with --control-dir ───────────────────────────────
   console.error(`\n🏎️  Running benchmarks (experiment vs control)…\n`);