* feat: AI-sorted PR review view with diff grouping
Group a PR's changed files into a logical top-to-bottom walkthrough via a best-effort structured-output LLM pass, kicked off concurrently with the reviewer run (~0 added latency) and persisted on reviewer thread metadata. Results render in the review UI behind an AI sorted / file tree toggle that persists across PRs; the view falls back to the file tree when groups are absent or stale.
Adds a grouping-model team default (inherits the Reviewer subagent model when unset) and the admin RolePicker for it.
* feat(reviews): richer AI-sorted explanations + sidebar polish
Sidebar group rows get Devin-style spacing (dividers, padding), a per-group file list (click a file to jump to its diff), inline-code chips in titles, and an accent Read explanation link.
Group explanations are now rich markdown: the grouping prompt feeds per-hunk line ranges and asks for inline code, a short code block, and [path:line](#loc=...) references. The Markdown renderer turns those #loc= links into in-page buttons that scroll the diff to the hunk and highlight the range, reusing the existing selectedLines path.
* fix(reviews): drop stale diff groups from the AI-sorted view
When groups were generated for a previous head, a persisted "ai" view in localStorage still rendered the outdated walkthrough. groupedView now returns null on diff_groups_stale, so the file-tree fallback is used and the view toggle hides until fresh groups arrive.
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Co-authored-by: open-swe[bot] <open-swe@users.noreply.github.com>
