feat(github): pull request tool window, timeline and review flow (#477)

Replaces the Pull Requests tool window with a full review workflow on top of gh's authentication.

- List with search, quick filters and paging; a tab per pull request and a New Pull Request tab.
- Details: commit picker, changes tree with viewed state, CI and reviewer status, merge, close and reopen.
- Timeline editor: comments, review threads, reactions and suggested changes.
- Review in the diff viewer and, for the checked-out branch, in the editor (review mode).
- New generic vcs extension points: registerDiffViewerProvider, lineInlays, reviewGutter, branch widget extensions; new vcs_merge_base and gh_api commands.
- CSP: img-src allows https://avatars.githubusercontent.com for avatars.

Fixed while testing against a real repository: remotes behind an SSH host alias, mergeability stuck on UNKNOWN, Apply Locally staying disabled after a checkout, relative links navigating the app's page, and review inlays wider than the pane.

Co-authored-by: imacross <[email protected]>

src/features/github/diff/settings.ts

@@ -0,0 +1,56 @@
+/**
+ * Review-in-diff settings, persisted in local storage: "Show Review Threads"
+ * (`GithubPullRequestsProjectUISettings.editorReviewViewOption`), the new comment's preferred
+ * button (`reviewCommentsPreferred`) and "Automatically mark opened files as viewed"
+ * (`GithubSettings.isAutomaticallyMarkAsViewed`, on Settings › Version Control › GitHub).
+ */
+import { create } from "zustand";
+import { THREADS_VIEW_OPTIONS, type ThreadsViewOption } from "./model";
+
+export interface ReviewDiffSettings {
+  threadsView: ThreadsViewOption;
+  /** "Start Review" is the primary button of a new comment (else "Add Single Comment"). */
+  reviewCommentsPreferred: boolean;
+  autoMarkViewed: boolean;
+}
+
+const KEY = "openidea.github.reviewDiff.v1";
+
+/** IntelliJ's defaults. */
+const DEFAULTS: ReviewDiffSettings = {
+  threadsView: "unresolved",
+  reviewCommentsPreferred: true,
+  autoMarkViewed: false,
+};
+
+export function parseReviewDiffSettings(raw: unknown): ReviewDiffSettings {
+  const o = raw && typeof raw === "object" ? (raw as Record<string, unknown>) : {};
+  const bool = (v: unknown, d: boolean) => (typeof v === "boolean" ? v : d);
+  return {
+    threadsView: THREADS_VIEW_OPTIONS.some((x) => x.value === o.threadsView)
+      ? (o.threadsView as ThreadsViewOption)
+      : DEFAULTS.threadsView,
+    reviewCommentsPreferred: bool(o.reviewCommentsPreferred, DEFAULTS.reviewCommentsPreferred),
+    autoMarkViewed: bool(o.autoMarkViewed, DEFAULTS.autoMarkViewed),
+  };
+}
+
+function load(): ReviewDiffSettings {
+  try {
+    const raw = globalThis.localStorage?.getItem(KEY);
+    return parseReviewDiffSettings(raw ? JSON.parse(raw) : null);
+  } catch {
+    return DEFAULTS;
+  }
+}
+
+export const useReviewDiffSettings = create<ReviewDiffSettings>(load);
+
+export function setReviewDiffSettings(patch: Partial<ReviewDiffSettings>) {
+  useReviewDiffSettings.setState(patch);
+  try {
+    globalThis.localStorage?.setItem(KEY, JSON.stringify(useReviewDiffSettings.getState()));
+  } catch {
+    /* storage unavailable */
+  }
+}