Merge main; keep inline panels polling while their host reports them hidden

Main now has #1282, which pauses periodic layer polling in a hidden page
with its own catch-up and listener cleanup, so this PR drops its duplicate
lifecycle.js change and test in favor of main's.

Review fixes:
- data.js passes panelAwareVisibility(document) (new in app/embed.js) as
  the lifecycle's visibility target, so an inline panel whose host reports
  it hidden keeps polling. The HUD's 250 ms readout follows the same
  document.hidden && !isEmbeddedInline() rule as tools.js.
- Tests: embed.test.mjs (layers poll in an inline panel reported hidden,
  pause without the flag) and hudPageVisibility.test.mjs (HUD readout).
  Both use mock timers and clean up in finally.
- changelog.d/1344-inline-panel-visibility.md and a note in
  docs/CURRENT-STATE.md.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

changelog.d/1344-inline-panel-visibility.md

@@ -0,0 +1,4 @@
+- Pause the HUD's camera readout while the page is hidden, as polled layers
+  already do. An app embedded inline in a panel keeps both updating, because the
+  panel's host can report the page as hidden while it is on screen (nu-stats,
+  #1344).