refactor(model-fallback): fully encapsulate session state in factory closure

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

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

src/plugin/tool-registry.ts

@@ -144,7 +144,7 @@ export function trimToolsToCap(filteredTools: ToolsRecord, maxTools: number): vo
 export function createToolRegistry(args: {
   ctx: PluginContext
   pluginConfig: OhMyOpenCodeConfig
-  managers: Pick<Managers, "backgroundManager" | "tmuxSessionManager" | "skillMcpManager">
+  managers: Pick<Managers, "backgroundManager" | "tmuxSessionManager" | "skillMcpManager" | "modelFallbackControllerAccessor">
   skillContext: SkillContext
   availableCategories: AvailableCategory[]
   interactiveBashEnabled?: boolean
@@ -170,6 +170,7 @@ export function createToolRegistry(args: {
     pluginConfig.disabled_agents ?? [],
     pluginConfig.agents,
     pluginConfig.categories,
+    managers.modelFallbackControllerAccessor,
   )
 
   const isMultimodalLookerEnabled = !(pluginConfig.disabled_agents ?? []).some(
@@ -191,6 +192,7 @@ export function createToolRegistry(args: {
     availableSkills: skillContext.availableSkills,
     sisyphusAgentConfig: pluginConfig.sisyphus_agent,
     syncPollTimeoutMs: pluginConfig.background_task?.syncPollTimeoutMs,
+    modelFallbackControllerAccessor: managers.modelFallbackControllerAccessor,
     onSyncSessionCreated: async (event) => {
       log("[index] onSyncSessionCreated callback", {
         sessionID: event.sessionID,