Diff hunks + thread context on review comments; preview env links; hide matrix placeholder

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DgBEW6qAwgn2fcQbA2f4ZQ

shared/types.ts

@@ -36,6 +36,9 @@ export interface PrSnapshot {
   isDraft: boolean;
   branch: string;
   updatedAt: string;
+  labels: string[];
+  /** Per-PR review environment, when the repo configures one and the label matches. */
+  previewUrl: string | null;
   reviewState: ReviewState;
   unresolvedThreads: number;
   totalThreads: number;
@@ -59,6 +62,8 @@ export interface TimelineEvent {
   reviewState: string | null;
   path: string | null;
   read: boolean;
+  /** Trailing lines of the diff hunk a review comment is anchored to. */
+  diffHunk: string | null;
   /** Set when this is a reply within a review thread: the thread's root comment. */
   inReplyTo: { actor: string; bodyExcerpt: string } | null;
 }