fix(FN-3794): pass unload context and isolate WhatsApp sessions per project

- Extend PluginOnUnload to receive runtime context and wire ctx through plugin-loader unload hooks
- Scope WhatsApp chat plugin connections by project root to avoid cross-project session leakage
- Update plugin authoring docs and add a patch changeset for @runfusion/fusion
- Align plugin test suites across WhatsApp and example/runtime plugins with the new onUnload context contract

Fusion-Task-Id: FN-3794

plugins/examples/fusion-plugin-ci-status/src/__tests__/index.test.ts

@@ -185,7 +185,7 @@ describe("ci-status plugin", () => {
       await plugin.hooks.onLoad?.(ctx as any);
       vi.clearAllMocks();
 
-      await plugin.hooks.onUnload?.();
+      await plugin.hooks.onUnload?.(ctx as any);
 
       expect(ctx.logger.info).toHaveBeenCalledWith("CI Status plugin unloaded");
     });