fix(kitojs): correct route chaining overloads and fix schema application

[skick1234]

Issue

• Validation is not applied when using route chaining with (handler, schema)

app.route('/api/secure').get((ctx) => {
  ctx.res.send('Success');
}, schema({
  query: t.object({ token: t.str() })
}));

Changes

• Used type narrowing to explicitly detect if the input is a handler or a schema, ensuring validation data always reaches the server.
• Add test cases for route chaining