feat(dashboard,sse): add OpenCode Free provider (noAuth, public endpoint)

Adds 'opencode' to FREE_PROVIDERS as a no-auth provider using the public
OpenCode endpoint (https://opencode.ai/zen/v1). The existing OpencodeExecutor
already skips the Authorization header when no API key is present. Registry
entry reuses the opencode executor and shares models from the zen/v1 endpoint.

open-sse/config/providerRegistry.ts

@@ -1034,6 +1034,30 @@ export const REGISTRY: Record<string, RegistryEntry> = {
     ],
   },
 
+  opencode: {
+    id: "opencode",
+    alias: "oc",
+    format: "openai",
+    executor: "opencode",
+    baseUrl: "https://opencode.ai/zen/v1",
+    modelsUrl: "https://opencode.ai/zen/v1/models",
+    authType: "apikey",
+    authHeader: "Authorization",
+    authPrefix: "Bearer",
+    defaultContextLength: 200000,
+    models: [
+      { id: "big-pickle", name: "Big Pickle" },
+      { id: "minimax-m2.5-free", name: "MiniMax M2.5 Free", contextLength: 204800 },
+      { id: "ling-2.6-1t-free", name: "Ling 2.6 Free", contextLength: 262000 },
+      {
+        id: "trinity-large-preview-free",
+        name: "Trinity Large Preview Free",
+        contextLength: 131000,
+      },
+      { id: "nemotron-3-super-free", name: "Nemotron 3 Super Free", contextLength: 1000000 },
+    ],
+  },
+
   "opencode-go": {
     id: "opencode-go",
     alias: "opencode-go",

src/shared/constants/providers.ts

@@ -34,6 +34,22 @@ export const FREE_PROVIDERS = {
     authHint:
       "Uses the same AWS Builder ID or imported refresh-token flow as Kiro, but keeps Amazon Q connections separate.",
   },
+  opencode: {
+    id: "opencode",
+    alias: "oc",
+    name: "OpenCode Free",
+    icon: "terminal",
+    color: "#E87040",
+    textIcon: "OC",
+    website: "https://opencode.ai",
+    noAuth: true,
+    authHint: "No API key required — uses OpenCode's public free endpoint.",
+    freeNote:
+      "No API key required — public OpenCode endpoint with Kimi, GLM, Qwen, MiMo, MiniMax models.",
+    notice: {
+      text: "OpenCode Free uses the public OpenCode endpoint (https://opencode.ai/zen/v1). No signup or API key needed. Rate limits apply.",
+    },
+  },
 };
 
 export const FREE_APIKEY_PROVIDER_IDS = new Set(["qoder"]);