refactor(core): split index.ts and config-handler.ts into focused modules

Main entry point:
- create-hooks.ts, create-tools.ts, create-managers.ts
- plugin-interface.ts: plugin interface types
- plugin/ directory: plugin lifecycle modules

Config handler:
- agent-config-handler.ts, command-config-handler.ts
- tool-config-handler.ts, mcp-config-handler.ts
- provider-config-handler.ts, category-config-resolver.ts
- agent-priority-order.ts, prometheus-agent-config-builder.ts
- plugin-components-loader.ts

src/plugin/types.ts

@@ -0,0 +1,15 @@
+import type { Plugin, ToolDefinition } from "@opencode-ai/plugin"
+
+export type PluginContext = Parameters<Plugin>[0]
+export type PluginInstance = Awaited<ReturnType<Plugin>>
+export type PluginInterface = Omit<PluginInstance, "experimental.session.compacting"> 
+
+export type ToolsRecord = Record<string, ToolDefinition>
+
+export type TmuxConfig = {
+  enabled: boolean
+  layout: "main-horizontal" | "main-vertical" | "tiled" | "even-horizontal" | "even-vertical"
+  main_pane_size: number
+  main_pane_min_width: number
+  agent_pane_min_width: number
+}