feat: add Z.ai GLM Coding Plan as built-in provider

Add native support for Z.ai's GLM Coding Plan subscription service,
enabling users to use GLM-5.1, GLM-5-Turbo, GLM-4.7, and GLM-4.5-Air
models directly from the onboarding UI.

Changes:
- Add 'zai' to SUPPORTED_ONBOARDING_PROVIDERS
- Add zai entry to BUILTIN_PROVIDERS (wire: anthropic)
- Add zai entry to PROVIDER_SHORTLIST with key help URL
- Add zai-glm preset to PROXY_PRESETS

Z.ai uses an Anthropic-compatible API endpoint
(https://api.z.ai/api/anthropic) designed for agentic coding tools,
matching the same integration pattern used by Claude Code.

Author: HEXA_E

packages/shared/src/config.ts

@@ -21,6 +21,7 @@ export const SUPPORTED_ONBOARDING_PROVIDERS = [
   'openai',
   'openrouter',
   'ollama',
+  'zai',
 ] as const;
 export type SupportedOnboardingProvider = (typeof SUPPORTED_ONBOARDING_PROVIDERS)[number];
 
@@ -294,6 +295,23 @@ export const BUILTIN_PROVIDERS: Readonly<Record<SupportedOnboardingProvider, Pro
       modelDiscoveryMode: 'models',
     },
   },
+  zai: {
+    id: 'zai',
+    name: 'Z.ai (GLM Coding Plan)',
+    builtin: true,
+    wire: 'anthropic',
+    baseUrl: 'https://api.z.ai/api/anthropic',
+    defaultModel: 'glm-5.1',
+    modelsHint: ['glm-5.1', 'glm-5-turbo', 'glm-4.7', 'glm-4.5-air'],
+    requiresApiKey: true,
+    capabilities: {
+      supportsKeyless: false,
+      supportsModelsEndpoint: false,
+      supportsReasoning: true,
+      requiresClaudeCodeIdentity: false,
+      modelDiscoveryMode: 'static-hint',
+    },
+  },
 } as const;
 
 // ── ConfigSchema v3 — canonical on-disk shape ────────────────────────────────
@@ -514,6 +532,13 @@ export const PROVIDER_SHORTLIST: Record<SupportedOnboardingProvider, ProviderSho
     primary: [OLLAMA_DEFAULT_MODEL, 'llama3.1', 'qwen2.5'],
     defaultPrimary: OLLAMA_DEFAULT_MODEL,
   },
+  zai: {
+    provider: 'zai',
+    label: 'Z.ai (GLM Coding Plan)',
+    keyHelpUrl: 'https://z.ai/manage-apikey/apikey-list',
+    primary: ['glm-5.1', 'glm-5-turbo', 'glm-4.7', 'glm-4.5-air'],
+    defaultPrimary: 'glm-5.1',
+  },
 };
 
 export function isSupportedOnboardingProvider(p: string): p is SupportedOnboardingProvider {

packages/shared/src/proxy-presets.ts

@@ -59,6 +59,13 @@ export const PROXY_PRESETS = [
     baseUrl: 'http://127.0.0.1:8317',
     notes: '',
   },
+  {
+    id: 'zai-glm',
+    label: 'Z.ai GLM Coding Plan',
+    provider: 'anthropic',
+    baseUrl: 'https://api.z.ai/api/anthropic',
+    notes: 'GLM-5.1, GLM-5-Turbo, GLM-4.7, GLM-4.5-Air',
+  },
   {
     id: 'custom',
     label: 'Custom...',