feat(cli): add doctor check for model resolution

Add new 'model-resolution' check to diagnose model fallback chain health. Validates that configured agents and categories can resolve to available models, surfacing misconfiguration early.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/cli/doctor/checks/index.ts

@@ -2,6 +2,7 @@ import type { CheckDefinition } from "../types"
 import { getOpenCodeCheckDefinition } from "./opencode"
 import { getPluginCheckDefinition } from "./plugin"
 import { getConfigCheckDefinition } from "./config"
+import { getModelResolutionCheckDefinition } from "./model-resolution"
 import { getAuthCheckDefinitions } from "./auth"
 import { getDependencyCheckDefinitions } from "./dependencies"
 import { getGhCliCheckDefinition } from "./gh"
@@ -12,6 +13,7 @@ import { getVersionCheckDefinition } from "./version"
 export * from "./opencode"
 export * from "./plugin"
 export * from "./config"
+export * from "./model-resolution"
 export * from "./auth"
 export * from "./dependencies"
 export * from "./gh"
@@ -24,6 +26,7 @@ export function getAllCheckDefinitions(): CheckDefinition[] {
     getOpenCodeCheckDefinition(),
     getPluginCheckDefinition(),
     getConfigCheckDefinition(),
+    getModelResolutionCheckDefinition(),
     ...getAuthCheckDefinitions(),
     ...getDependencyCheckDefinitions(),
     getGhCliCheckDefinition(),