fix: removing a loaded <webview> threw "Invalid guestInstanceId" - #54089

* Electron 45 beta so Google's sign-in accepts Work again

Chrome 156 is stable and Google's sign-in now refuses Work ("This browser
or app may not be secure"). Every Electron 44 release, 44.7.0 included,
carries Chromium 152; Electron 45.0.0-beta.1 carries Chromium
156.0.8078.12. The app already presents as plain Chrome, so the engine
version was the gap. The beta is pinned exactly.

- Screen sharing: Electron 45 reports getDisplayMedia to the permission
  handler as display-capture instead of media with no media types. The
  share picker now runs on display-capture, a granted share keeps the
  page awake as before, and media maps only to camera and microphone.
- Electron 45.0.0-beta.1 carries the Invalid guestInstanceId fix
  (electron/electron#54089, backport #54096), so the renderer guard and
  the e2e harness filter are gone (ADR 0150, TODO.md).
- node-abi 4.37.0 in the lockfile so @electron/rebuild maps Electron 45
  to its ABI (150); 4.33.0 reported 149.
- ADR 0150 records the upgrade and why; DESIGN.md entry for 2026-10-09.

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

* Present Chrome's reduced user agent, and check what a page sees

Chrome's user agent names only its major version (Chrome/156.0.0.0);
Electron's carries the full one, which no Chrome sends. The fallback UA now
reduces it, and the full-version client hint takes the engine's real
version from process.versions.chrome instead of the UA.

browser-identity.e2e.ts checks a page's view: the request's User-Agent,
and in JavaScript the user agent, its brands and the full version list.
TODO.md records the stable pin and the async safeStorage follow-up.

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

* Build Chrome's brand list the way Chromium does, and record the gaps

The placeholder brand was Chrome 150's ("Not;A=Brand") in a fixed order.
shared/chrome-brands.ts builds the list as Chromium's
GetGreasedUserAgentBrandVersion does, seeded by the major version, so
Chrome 156 is "Not:A-Brand";v="8", "Chromium";v="156",
"Google Chrome";v="156" in the header, navigator.userAgentData.brands
and its toJSON() alike (toJSON read Chromium's own list). Main and the
preload share it, from process.versions.chrome.

ADR 0150 and DESIGN.md record the reduced user agent and that headers are
not a full match (page loads carry no client hints). TODO.md: the
safeStorage entry covers isEncryptionAvailable and Electron 46's removal;
new follow-ups for page-load client hints and the legacy chromeMediaSource
capture path.

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

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Co-authored-by: Claude Opus 5.5 <[email protected]>