* fix(browser): stop impersonating the source browser's UA on cookie import (STA-3514)
Delete the import-time UA synthesis entirely instead of patching its version
detection. The session now always keeps the engine-derived UA the registry
sets at startup (clean or native), for imported and non-imported profiles
alike.
Why deletion is the fix:
- The synthesis read CFBundleShortVersionString, which on forks is a
marketing version — Arc imports presented Chrome/1.x and sites rejected
the browser as ancient (STA-3514).
- Its stated purpose (keep Google-bound cookies valid) is handled by
isGoogleSourceBoundCookie excluding those cookies since #736, and #12884
measured that Google rejects re-transplants regardless of UA identity.
- #12608 measured the synthesized Chrome-shaped UA reaching
/v3/signin/rejected while the engine UA reached account lookup.
Persisted userAgent/userAgentByPartition meta is no longer read; legacy keys
drop off on the next meta write. The #12811 gate existed only to catch bad
synthesized values, so it leaves with the synthesis.
* test(browser): catch source UA impersonation regression
Brennan Benson
c03c01ad15