test(web): retain failed foreground activation control

A successful lifecycle resume leaves the diagnostic target hidden. Add an opt-in tab activation observation with explicit visibility and focus assertions so it cannot be mistaken for foreground convergence. Preserve both failed runs and the short timer-sampling limitation; no application or release qualification is claimed.

Change-source: pulse-maintainer

frontend-modern/browser-tests/lifecycle-control.md

@@ -60,3 +60,40 @@ a Playwright page attachment may reintroduce the confounder. Before testing
 foreground convergence, separately observe return to visible. Installed acceptance
 still requires the authorised synthetic installation and exact byte identities
 listed in `alert-recovery-acceptance.md`; neither is supplied by this control.
+
+## Foreground activation control — 8 September 2026
+
+`pulse-heavy-run -- node scripts/check-browser-single-session-control.mjs --foreground`
+adds `Page.bringToFront` after the separate post-resume snapshot, then takes a
+foreground snapshot after 250ms. Default invocation retains the original
+freeze/resume-only behaviour. The optional mode requires visible **and** focused
+state plus timer progress; it does not force focus emulation back on to obtain a
+passing result. No Playwright page is attached.
+
+Fresh [CDP documentation](https://chromedevtools.github.io/devtools-protocol/tot/Page/#method-bringToFront)
+describes tab activation separately from lifecycle state. The command's success
+is not evidence of visibility restoration. On the same Chrome revision and
+runtime listed above, both the initial implementation and the final optional-mode
+run exited 1:
+
+- Forced-focus negative: ticks 5 → 52 → 57; visible/focused throughout, no events.
+- Unforced positive: freeze and resume at tick 5, hidden/unfocused after resume;
+  after activation, **hidden/focused**, without a visible visibilitychange event.
+- The first run stayed at tick 5 through the foreground sample; the optional-mode
+  run reached tick 6 only at that final sample. Both failed the earlier
+  post-resume timer-progress assertion before reaching the foreground assertion.
+
+The 250ms post-resume sample is therefore not a dependable timer-progress bound
+for this hidden target. Do not interpret that failed assertion as missing resume:
+ordered freeze/resume events were recorded. Independently, visibility restoration
+failed in both observed foreground samples. Neither threshold was relaxed and
+neither failure is cleared by the earlier successful freeze-only control.
+
+No Pulse fixture was exercised: the prerequisite foreground control is still
+unestablished. Before applying this arrangement to application convergence,
+choose and verify an actual visibility transition (potentially a headed browser
+with owned window activation), retaining the suspension probe and all failed
+observations. Repeating this activation unchanged, synthetically dispatching a
+visibility event, or enabling forced focus would not resolve the evidence gap.
+This diagnostic is not a release gate and proves nothing about installed
+incident state or destination receipt.

scripts/check-browser-single-session-control.mjs

@@ -6,6 +6,7 @@ import { tmpdir } from 'node:os';
 import { join } from 'node:path';
 import { createRequire } from 'node:module';
 import { chromium } from '@playwright/test';
+const checkForeground = process.argv.includes('--foreground');
 const wait = ms => new Promise(resolve => setTimeout(resolve, ms));
 const profile = await mkdtemp(join(tmpdir(), 'pulse-lifecycle-'));
 const child = spawn(chromium.executablePath(), ['--headless', '--no-sandbox',
@@ -83,13 +84,26 @@ try {
       const resume = after.events.find(e => e.type === 'resume');
       const suspended = Boolean(freeze && resume && freeze.ticks === resume.ticks &&
         after.events.indexOf(freeze) < after.events.indexOf(resume) && after.ticks > resume.ticks);
-      const result = { focusEnabled, before, after, commands, suspended };
+      // Resume is not foreground activation. Observe the two transitions separately.
+      let foreground;
+      if (checkForeground) {
+        await command('Page.bringToFront', {});
+        await wait(250);
+        foreground = await evaluate(snapshot);
+      }
+      const result = { focusEnabled, before, after, foreground, commands, suspended };
       results.push(result); console.log(JSON.stringify(result));
     } finally { await send('Target.closeTarget', { targetId }); }
   }
   assert.ok(!results[0].suspended && results[0].after.ticks - results[0].before.ticks >= 20,
     'Negative control must continue ticking');
   assert.ok(results[1].suspended, 'Positive control must suspend and resume timers');
+  if (checkForeground) {
+    assert.ok(results[1].foreground.visibility === 'visible' && results[1].foreground.focus,
+      'Positive control must return to visible and focused after tab activation');
+    assert.ok(results[1].foreground.ticks > results[1].after.ticks,
+      'Foreground timer must continue advancing');
+  }
 } finally {
   socket?.close();
   const exited = new Promise(resolve => child.once('exit', resolve));