fix(config): clear stale context limit cache on provider updates

Rebuilding provider model limits prevents removed entries from leaking into later compaction decisions after config changes.

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

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

src/plugin-handlers/provider-config-handler.ts

@@ -33,6 +33,9 @@ export function applyProviderConfig(params: {
   const providers = params.config.provider as
     | Record<string, ProviderConfig>
     | undefined;
+  const modelContextLimitsCache = params.modelCacheState.modelContextLimitsCache;
+
+  modelContextLimitsCache.clear()
 
   const anthropicBeta = providers?.anthropic?.options?.headers?.["anthropic-beta"];
   params.modelCacheState.anthropicContext1MEnabled =
@@ -61,7 +64,7 @@ export function applyProviderConfig(params: {
       const contextLimit = modelConfig?.limit?.context;
       if (!contextLimit) continue;
 
-      params.modelCacheState.modelContextLimitsCache.set(
+      modelContextLimitsCache.set(
         `${providerID}/${modelID}`,
         contextLimit,
       );