feat(copilot): add GitHub Enterprise Server support (#2175)

* feat(copilot): add GitHub Enterprise Server support

* fix(copilot): address GHES PR review findings (P1 + 2×P2)

- P1: Use composite account ID (domain:user_id) for GHES to prevent
  cross-instance ID collisions; github.com keeps plain numeric ID for
  backward compatibilit
- P2-a: Use get_api_endpoint() for model list URL with automatic
  fallback to static URL when dynamic endpoint resolution fails
- P2-b: Add normalize_github_domain() as backend SSOT for domain
  normalization (lowercase, strip protocol/path/query, reject userinfo)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

src/lib/api/auth.ts

@@ -9,6 +9,7 @@ export interface ManagedAuthAccount {
   avatar_url: string | null;
   authenticated_at: number;
   is_default: boolean;
+  github_domain: string;
 }
 
 export interface ManagedAuthStatus {
@@ -30,19 +31,23 @@ export interface ManagedAuthDeviceCodeResponse {
 
 export async function authStartLogin(
   authProvider: ManagedAuthProvider,
+  githubDomain?: string,
 ): Promise<ManagedAuthDeviceCodeResponse> {
   return invoke<ManagedAuthDeviceCodeResponse>("auth_start_login", {
     authProvider,
+    githubDomain: githubDomain || null,
   });
 }
 
 export async function authPollForAccount(
   authProvider: ManagedAuthProvider,
   deviceCode: string,
+  githubDomain?: string,
 ): Promise<ManagedAuthAccount | null> {
   return invoke<ManagedAuthAccount | null>("auth_poll_for_account", {
     authProvider,
     deviceCode,
+    githubDomain: githubDomain || null,
   });
 }
 

src/lib/api/copilot.ts

@@ -30,6 +30,8 @@ export interface GitHubAccount {
   avatar_url: string | null;
   /** 认证时间戳（Unix 秒） */
   authenticated_at: number;
+  /** GitHub 域名（github.com 或 GHES 域名） */
+  github_domain: string;
 }
 
 /**