Auto-attach pasted GitHub PR/issue URLs in the composer (#1006)

* Auto-attach pasted GitHub PR/issue URLs in the composer

Paste a GitHub PR or issue link into any composer and it shows up
as an attachment pill within a debounce tick when the URL matches
the workspace's remote. On the new-workspace screen, an attached PR
also surfaces an inline "Check out PR #N?" hint next to the picker;
one click promotes it to the checkout target through the same
syncPickerPrAttachment flow the dropdown uses.

Unifies the new-workspace picker and composer attachment picker on
one shared GitHub search hook and cache key, so both consumers (and
the auto-attach lookup) share the React Query cache.

* Fix oxfmt formatting in new-workspace-screen import

packages/app/src/git/use-github-search-query.ts

@@ -0,0 +1,64 @@
+import { useQuery } from "@tanstack/react-query";
+import type { GitHubSearchRequest, GitHubSearchResponse } from "@server/shared/messages";
+
+export const GITHUB_SEARCH_STALE_TIME = 30_000;
+
+export type GitHubSearchPayload = GitHubSearchResponse["payload"];
+
+export interface GitHubSearchClient {
+  searchGitHub: (
+    options: {
+      cwd: string;
+      query: string;
+      limit?: number;
+      kinds?: GitHubSearchRequest["kinds"];
+    },
+    requestId?: string,
+  ) => Promise<GitHubSearchPayload>;
+}
+
+interface GitHubSearchQueryInput {
+  client: GitHubSearchClient | null;
+  serverId: string;
+  cwd: string;
+  query: string;
+  kinds?: GitHubSearchRequest["kinds"];
+  enabled: boolean;
+}
+
+export function githubSearchQueryKey(
+  serverId: string,
+  cwd: string,
+  query: string,
+  kinds?: GitHubSearchRequest["kinds"],
+) {
+  const trimmedQuery = query.trim();
+  if (!kinds) {
+    return ["github-search", serverId, cwd, trimmedQuery] as const;
+  }
+  return ["github-search", serverId, cwd, trimmedQuery, [...kinds].sort().join(",")] as const;
+}
+
+export function buildGithubSearchQueryOptions(input: GitHubSearchQueryInput) {
+  const query = input.query.trim();
+
+  return {
+    queryKey: githubSearchQueryKey(input.serverId, input.cwd, query, input.kinds),
+    queryFn: async (): Promise<GitHubSearchPayload> => {
+      if (!input.client) {
+        throw new Error("Host is not connected");
+      }
+      const request = { cwd: input.cwd, query, limit: 20 };
+      if (input.kinds) {
+        return input.client.searchGitHub({ ...request, kinds: input.kinds });
+      }
+      return input.client.searchGitHub(request);
+    },
+    enabled: input.enabled && Boolean(input.client),
+    staleTime: GITHUB_SEARCH_STALE_TIME,
+  };
+}
+
+export function useGithubSearchQuery(input: GitHubSearchQueryInput) {
+  return useQuery(buildGithubSearchQueryOptions(input));
+}