Move auto-review into the runtime (PR #615)

[TyroneNel]

Auto-review currently only runs while a browser tab is open (see bug #614). PR #615 proposes moving the auto-review loop into the runtime as a reconciler so boards advance unattended and recover after restarts.

This is a behavioural change, and feature pull requests are not being accepted during research preview, so this discussion exists as a low-cost place to respond if the PR is not wanted yet: preferences on scope, timing, or alternative designs are all welcome.

• Bug: Auto-review stops and discards pending actions when the browser tab closes #614
• PR: fix(auto-review): run the auto-review loop in the runtime #615 (depends on fix(auto-review): persist pending git action so review cards can't strand #613)