Release v0.52.0 - #95

…ey test RP

plans/cmux-next/passkeys.md proposes Chrome-parity passkeys for CEF and
WebKit panes. Its "Known bugs: do not repeat" table lists every passkey bug
in the old app and repo history (K1-K18) with symptom, root cause, fix
status and the regression test each engine needs. New findings: cmux next
lost the whole WebKit passkey bridge with the legacy deletion on
2026-09-29 (#15659), so WebKit panes are back to "partial passkey support"
and the #9060/#15525 fixes are gone; the RC channel ships without the
passkey entitlement (verified on the installed 0.65.0-rc); three fixes on
main never merged (#6766 hybrid routing, #8630 private-selector crash,
#9529 leaked presentation windows); the bridge was silently dropped for ten
weeks by cb1a6de; the bridge ignores AbortSignal; Chromium refuses
WebAuthn in a tab that is not VISIBLE (cmux-browser #95), which applies to
our CEF occlusion and hibernation.

tests/passkeys: a local relying party (index.html, frame.html on
frame.localhost for cross-origin iframes, scenarios.js) and run.mjs, which
runs 17 scenarios in Chromium with a DevTools virtual authenticator. Stock
Chrome for Testing 153.0.8010.12 passes 17/17 (16 judged, 1 record-only);
the same runner targets a cmux CEF instance with --cdp, and --serve serves
the page for manual runs.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>