feat: implement default Git identity management and local identity check

packages/ui/src/lib/api/types.ts

@@ -294,6 +294,7 @@ export interface GitAPI {
   getGitLog(directory: string, options?: GitLogOptions): Promise<GitLogResponse>;
   getCommitFiles(directory: string, hash: string): Promise<GitCommitFilesResponse>;
   getCurrentGitIdentity(directory: string): Promise<GitIdentitySummary | null>;
+  hasLocalIdentity?(directory: string): Promise<boolean>;
   setGitIdentity(directory: string, profileId: string): Promise<{ success: boolean; profile: GitIdentityProfile }>;
   getGitIdentities(): Promise<GitIdentityProfile[]>;
   createGitIdentity(profile: GitIdentityProfile): Promise<GitIdentityProfile>;

packages/ui/src/lib/desktop.ts

@@ -56,6 +56,7 @@ export type DesktopSettings = {
   defaultModel?: string; // format: "provider/model"
   defaultVariant?: string;
   defaultAgent?: string;
+  defaultGitIdentityId?: string; // ''/undefined = unset, 'global' or profile id
   autoCreateWorktree?: boolean;
   queueModeEnabled?: boolean;
   commitMessageModel?: string; // format: "provider/model"

packages/ui/src/lib/gitApi.ts

@@ -239,6 +239,12 @@ export async function getCurrentGitIdentity(directory: string): Promise<import('
   return gitHttp.getCurrentGitIdentity(directory);
 }
 
+export async function hasLocalIdentity(directory: string): Promise<boolean> {
+  const runtime = getRuntimeGit();
+  if (runtime?.hasLocalIdentity) return runtime.hasLocalIdentity(directory);
+  return gitHttp.hasLocalIdentity(directory);
+}
+
 export async function setGitIdentity(
   directory: string,
   profileId: string

packages/ui/src/lib/gitApiHttp.ts

@@ -516,6 +516,18 @@ export async function getCurrentGitIdentity(directory: string): Promise<GitIdent
   };
 }
 
+export async function hasLocalIdentity(directory: string): Promise<boolean> {
+  if (!directory) {
+    return false;
+  }
+  const response = await fetch(buildUrl(`${API_BASE}/has-local-identity`, directory));
+  if (!response.ok) {
+    throw new Error(`Failed to check local identity: ${response.statusText}`);
+  }
+  const data = await response.json().catch(() => null);
+  return data?.hasLocalIdentity === true;
+}
+
 export async function getGlobalGitIdentity(): Promise<GitIdentitySummary | null> {
   const response = await fetch(buildUrl(`${API_BASE}/global-identity`, undefined));
   if (!response.ok) {