feat(agent): unify MCP tools and adopt Responses delivery

Move project and host queries into native MCP with host-owned OAuth/context,
while retaining memory, skills, actions and publication plugins. Add nearby-model
queries and explicit chat/task/learning model defaults.

Adopt Responses HTTP/SSE and native steer/queue inbox delivery, preserving scoped
session ownership, pending input edits and investigation communication.

Disable local-provider discovery: Server /health allowed native vLLM to probe
/v1/models on port 8000. A native before/after regression prevents recurrence.

Validation: 170 focused Bun tests; service/plugin typechecks; native discovery,
provider-discovery and input-inbox smoke checks; no paid model inference.

src/chat/modelConfig.ts

@@ -17,7 +17,11 @@ const modelSchema = z.object({
   compatibility: z.record(z.unknown()).optional(),
 }).strict();
 const modelConfigSchema = z.object({
-  default_model: text, task_model: text.optional(), learning_gate_model: text.optional(),
+  defaults: z.object({
+    chat: text,
+    task: text,
+    learning_gate: text,
+  }).strict(),
   providers: z.record(z.object({
     name: text, api_url: text, api_key: text.optional(),
     package: text.default("@opencode/ai/providers/openai-compatible"),
@@ -55,7 +59,7 @@ export const getAgentModelIds = (options: AgentModelOption[]) => options.map((mo
 export function parseAgentModelConfig(input: unknown): AgentModelConfig {
   const parsed = modelConfigSchema.safeParse(input);
   // Do not echo invalid values: provider configuration can contain credentials.
-  if (!parsed.success) throw new Error("invalid agent model configuration structure");
+  if (!parsed.success) throw new Error("invalid agent model configuration structure; configure role models under defaults.chat, defaults.task and defaults.learning_gate");
   const configuration = parsed.data;
   for (const [id, provider] of Object.entries(configuration.providers)) {
     if (!/^[A-Za-z0-9_-]+$/.test(id)) throw new Error("provider ID must contain only letters, digits, _ or -");
@@ -72,10 +76,10 @@ export function parseAgentModelConfig(input: unknown): AgentModelConfig {
     for (const modelID of Object.keys(provider.models)) parseModelReference(`${id}/${modelID}`);
   }
   const allowed = getAgentModelIds(configuredToolModels(configuration));
-  for (const role of ["default_model", "task_model", "learning_gate_model"] as const) {
-    if (configuration[role] && !allowed.includes(configuration[role]!)) throw new Error(`${role} must name an enabled configured text model with tool support`);
+  for (const role of ["chat", "task", "learning_gate"] as const) {
+    if (!allowed.includes(configuration.defaults[role])) throw new Error(`defaults.${role} must name an enabled configured text model with tool support`);
   }
-  if (!getAgentModelIds(getAgentModelOptions(configuration)).includes(configuration.default_model)) throw new Error("default_model must be selectable in the chat catalog");
+  if (!getAgentModelIds(getAgentModelOptions(configuration)).includes(configuration.defaults.chat)) throw new Error("defaults.chat must be selectable in the chat catalog");
   return configuration;
 }
 
@@ -101,5 +105,5 @@ export function compileOpencodeModels(configuration: AgentModelConfig) {
       }])),
     }];
   }));
-  return { model: configuration.default_model, providers };
+  return { model: configuration.defaults.chat, providers };
 }