fix: verify demo bundle freshness for smokes too

Golden runs, benchmarks and documentation captures each called
assertFreshDemoBundle; the smoke launcher never did, so all ~128 smokes could
silently test a stale demo/srv/assets bundle. On #234 that cost a round of
analysis: three assertions went red and a fourth went green, because the old
code was wrong in two places that agreed with each other, and a mixed result
reads as a logic defect rather than a stale artefact.

launch() now runs the check once for every smoke, against the repository root
rather than the serving root — demo/srv has no src/** to fingerprint.
HP_ALLOW_STALE_BUNDLE=1 skips it for debugging and warns out loud, because a
guard that says nothing when it steps aside is the silent success this project
keeps removing. A mutation entry proves the call cannot quietly disappear.

Issue: #236
User-Visible: no

scripts/mutation-gate.mjs

@@ -81,6 +81,19 @@ export const MUTANTS = [
       replace: '  for (let i = 0; i < Math.min(count, (recorded?.length ?? 0)); i++) {',
     }],
   },
+  {
+    id: 'smoke-launcher-skips-freshness',
+    guard: 'node --test --test-name-pattern="launcher enforces the gate" '
+      + 'test/bundle-freshness.test.mjs',
+    because: 'a smoke run against a stale demo bundle does not fail cleanly — on #234 three '
+      + 'assertions went red while a fourth went green, because the old code was wrong in two '
+      + 'places that agreed with each other, and the mixed result reads as a logic defect (#236)',
+    patches: [{
+      file: 'demo/serve.mjs',
+      find: '  await assertFreshDemoBundleUnlessAllowed(page, REPO_ROOT);',
+      replace: '  // freshness intentionally skipped by the mutant',
+    }],
+  },
   {
     id: 'snapn-returns-input-near-node',
     guard: 'npx tsc -p tsconfig.test.json && node scripts/fix-test-build.mjs '
@@ -684,8 +697,8 @@ export const MUTANTS = [
       + 'changing the separate room-fill gradient',
     patches: [{
       file: 'src/device-presentation.ts',
-      find: '  if (lqi <= 40) return \'low\';',
-      replace: '  if (lqi < 40) return \'low\';',
+      find: '  if (lqi <= 40) return \\'low\\';',
+      replace: '  if (lqi < 40) return \\'low\\';',
     }],
   },
   {