feat(app,server): add pull request pane to the workspace sidebar

Introduce a PR tab in the explorer sidebar that shows status checks,
reviews, and the merged timeline for the current branch's pull
request. Extend checkout PR status with number, draft flag, repo
identity, and per-check workflow/duration; add a new
pull_request_timeline request/response pair backed by a GraphQL
query; enrich the workspace git snapshot to carry the fields through
to the client; and extend the checkout-git-actions store so timeline
queries are invalidated alongside status when mutations land.

packages/server/src/shared/messages.ts

@@ -1133,6 +1133,15 @@ export const CheckoutPrStatusRequestSchema = z.object({
   requestId: z.string(),
 });
 
+export const PullRequestTimelineRequestSchema = z.object({
+  type: z.literal("pull_request_timeline_request"),
+  cwd: z.string(),
+  prNumber: z.number(),
+  repoOwner: z.string(),
+  repoName: z.string(),
+  requestId: z.string(),
+});
+
 export const ValidateBranchRequestSchema = z.object({
   type: z.literal("validate_branch_request"),
   cwd: z.string(),
@@ -1554,6 +1563,7 @@ export const SessionInboundMessageSchema = z.discriminatedUnion("type", [
   CheckoutPushRequestSchema,
   CheckoutPrCreateRequestSchema,
   CheckoutPrStatusRequestSchema,
+  PullRequestTimelineRequestSchema,
   CheckoutSwitchBranchRequestSchema,
   StashSaveRequestSchema,
   StashPopRequestSchema,
@@ -2505,24 +2515,31 @@ export const CheckoutPrCreateResponseSchema = z.object({
   }),
 });
 
-const CheckoutPrStatusSchema = z.object({
+export const CheckoutPrStatusSchema = z.object({
+  number: z.number().optional(),
   url: z.string(),
   title: z.string(),
   state: z.string(),
   baseRefName: z.string(),
   headRefName: z.string(),
   isMerged: z.boolean(),
+  isDraft: z.boolean().optional().default(false),
   checks: z
     .array(
       z.object({
         name: z.string(),
         status: z.string(),
         url: z.string().nullable(),
+        workflow: z.string().optional(),
+        duration: z.string().optional(),
       }),
     )
-    .optional(),
+    .optional()
+    .default([]),
   checksStatus: z.string().optional(),
   reviewDecision: z.string().nullable().optional(),
+  repoOwner: z.string().optional(),
+  repoName: z.string().optional(),
 });
 
 export const CheckoutPrStatusResponseSchema = z.object({
@@ -2536,6 +2553,87 @@ export const CheckoutPrStatusResponseSchema = z.object({
   }),
 });
 
+const PullRequestTimelineKnownErrorSchema = z.discriminatedUnion("kind", [
+  z.object({
+    kind: z.literal("not_found"),
+    message: z.string().optional().default(""),
+  }),
+  z.object({
+    kind: z.literal("forbidden"),
+    message: z.string().optional().default(""),
+  }),
+  z.object({
+    kind: z.literal("unknown"),
+    message: z.string().optional().default(""),
+  }),
+]);
+
+const PullRequestTimelineErrorSchema = z.preprocess((value) => {
+  if (!value || typeof value !== "object" || Array.isArray(value)) {
+    return { kind: "unknown", message: "" };
+  }
+  const error = value as Record<string, unknown>;
+  if (error.kind === "not_found" || error.kind === "forbidden" || error.kind === "unknown") {
+    return error;
+  }
+  return { ...error, kind: "unknown" };
+}, PullRequestTimelineKnownErrorSchema);
+
+const PullRequestTimelineReviewItemSchema = z.object({
+  id: z.string().optional().default(""),
+  kind: z.literal("review"),
+  author: z.string().optional().default("unknown"),
+  body: z.string().optional().default(""),
+  createdAt: z.number().optional().default(0),
+  url: z.string().optional().default(""),
+  reviewState: z
+    .enum(["approved", "changes_requested", "commented"])
+    .optional()
+    .default("commented"),
+});
+
+const PullRequestTimelineCommentItemSchema = z.object({
+  id: z.string().optional().default(""),
+  kind: z.literal("comment"),
+  author: z.string().optional().default("unknown"),
+  body: z.string().optional().default(""),
+  createdAt: z.number().optional().default(0),
+  url: z.string().optional().default(""),
+});
+
+export const PullRequestTimelineItemSchema = z.preprocess(
+  (value) => {
+    if (!value || typeof value !== "object" || Array.isArray(value)) {
+      return value;
+    }
+    const item = value as Record<string, unknown>;
+    if (item.kind === "review" || item.kind === "comment") {
+      return item;
+    }
+    return { ...item, kind: "comment" };
+  },
+  z.discriminatedUnion("kind", [
+    PullRequestTimelineReviewItemSchema,
+    PullRequestTimelineCommentItemSchema,
+  ]),
+);
+
+export const PullRequestTimelineResponseSchema = z.object({
+  type: z.literal("pull_request_timeline_response"),
+  payload: z
+    .object({
+      cwd: z.string().optional().default(""),
+      prNumber: z.number().nullable().optional().default(null),
+      items: z.array(PullRequestTimelineItemSchema).optional().default([]),
+      truncated: z.boolean().optional().default(false),
+      error: PullRequestTimelineErrorSchema.nullable().optional().default(null),
+      requestId: z.string().optional().default(""),
+      githubFeaturesEnabled: z.boolean().optional().default(true),
+    })
+    .optional()
+    .default({}),
+});
+
 export const CheckoutSwitchBranchResponseSchema = z.object({
   type: z.literal("checkout_switch_branch_response"),
   payload: z.object({
@@ -3000,6 +3098,7 @@ export const SessionOutboundMessageSchema = z.discriminatedUnion("type", [
   CheckoutPushResponseSchema,
   CheckoutPrCreateResponseSchema,
   CheckoutPrStatusResponseSchema,
+  PullRequestTimelineResponseSchema,
   CheckoutSwitchBranchResponseSchema,
   StashSaveResponseSchema,
   StashPopResponseSchema,
@@ -3234,6 +3333,9 @@ export type CheckoutPrCreateRequest = z.infer<typeof CheckoutPrCreateRequestSche
 export type CheckoutPrCreateResponse = z.infer<typeof CheckoutPrCreateResponseSchema>;
 export type CheckoutPrStatusRequest = z.infer<typeof CheckoutPrStatusRequestSchema>;
 export type CheckoutPrStatusResponse = z.infer<typeof CheckoutPrStatusResponseSchema>;
+export type PullRequestTimelineRequest = z.infer<typeof PullRequestTimelineRequestSchema>;
+export type PullRequestTimelineItem = z.infer<typeof PullRequestTimelineItemSchema>;
+export type PullRequestTimelineResponse = z.infer<typeof PullRequestTimelineResponseSchema>;
 export type CheckoutSwitchBranchRequest = z.infer<typeof CheckoutSwitchBranchRequestSchema>;
 export type CheckoutSwitchBranchResponse = z.infer<typeof CheckoutSwitchBranchResponseSchema>;
 export type StashSaveRequest = z.infer<typeof StashSaveRequestSchema>;