RouteBuilder post-group modifier chaining bug (`middlewares`, `rateLimit`, `cacheable`)

[armanist]

Summary

RouteBuilder currently breaks when chaining multiple post-group modifiers on the same group result.

Example pattern:

$route->group('auth', function ($route) {
    // routes...
})->rateLimit(60, 60)->middlewares(['Auth']);

The second call throws:
rateLimit() must be called inside a group or after a route definition
(or analogous error depending on call order).

Root cause

RouteBuilder stores grouped routes in lastGroupRoutes, but each post-group modifier method consumes/clears this state after one call. As a result, chaining a second post-group modifier has no active group context.

Affected methods:

• middlewares()
• rateLimit()
• cacheable()

Expected behavior

Post-group modifiers should be chainable and order-independent for the same group result.

Both should work:

• ->middlewares(...)->rateLimit(...)
• ->rateLimit(...)->middlewares(...)
  (and with cacheable(...) combinations)

Scope

Core router fix in RouteBuilder + regression tests.

Acceptance criteria

• Chaining multiple post-group modifiers on one group no longer throws.
• All affected modifier combinations apply to the same grouped routes.
• Add regression tests covering:
  • group + middlewares + rateLimit (both orders)
  • group + cacheable + one of the above
• Existing route/group behavior remains unchanged for non-chained usage.

Note

This bug is currently blocking natural fluent usage in module templates and can surface during app boot when generated routes include chained post-group modifiers.