v0.22.3

fix: let guest users enter the app without starting a review

Previously `guestMode` only flipped when the user completed a local
review via LocalRepoDialog. Someone who arrived at the welcome screen
without a GitHub account and wasn't ready to start a diff was stuck.

Add a tertiary "Continue without signing in →" link under the two
paths. It flips `guestMode` and drops the user on the newspaper, where
they can browse history, open settings, and find the compose form
whenever they're ready. The "Reading locally · Connect GitHub →"
strip on the masthead gives them a one-click upgrade if they change
their mind.

Extract the flip + persist logic into enterGuestMode() so both entry
points share it.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>