feat(aop)!: first-class callable advices

[lisachenko]

What

Brings first-class callable advices into the framework as the main way advices are woven into generated code (supersedes the feature/direct-first-class-advices WIP branch, rebased onto master and reorganized into logical commits).

Generated proxies now reference each advice as a closure created with first-class callable syntax directly on the aspect instance:

static $__joinPoint = InterceptorInjector::forMethod(
    self::class,
    'doSomething',
    [
        Interceptor::before(The::aspect(MonitorAspect::class)->beforeMethodExecution(...)),
    ],
    $this->__aop__doSomething(...),
);

Advices registered in the container as plain closures (not aspect methods) are resolved lazily through the new The::advice('advisorId') accessor, which unwraps Advisor/interceptor values down to the raw advice closure.

Commits

1. feat(aop): generate first-class advice callables — the proxy generation switch: The/Interceptor facades, GeneratedInterceptor descriptors, InterceptorListGenerator, removal of LazyAdvisorAccessor (rebased onto current master, adapting master's newer fixtures/tests).
2. feat(aop)!: replace advice marker interfaces with AdviceTypeEnum — drops AdviceBefore/AdviceAfter/AdviceAround; Advice::getType(): AdviceTypeEnum now carries the advice kind and its sorting priority.
3. feat(aop)!: require aspect advice methods to be public — FCC wiring calls advice methods on the aspect instance from generated code, so the attribute loader rejects non-public advice methods with an AspectException (methods with only #[Pointcut] keep any visibility).
4. feat(aop): resolve closure advices through The::advice() accessor — container-backed closure advices become weavable; joinpoint flattening rejects non-Advice advisor values loudly; GeneratedInterceptor::fromAdvisorId() removed.
5. docs: document first-class callable advices — CHANGELOG 4.0.0 entries and README rework presenting FCC advices as the main approach.
6. docs: refresh AGENTS.md for first-class callable advice wiring — agent guides updated to the new proxy dispatch and advice-wiring components.

BC breaks

• Aspect advice methods (#[Before], #[After], #[Around], #[AfterThrowing]) must be public.
• AdviceBefore/AdviceAfter/AdviceAround marker interfaces removed; every Advice implementation must implement getType(): AdviceTypeEnum.

Testing

• ./vendor/bin/phpunit — 2609 tests, 3216 assertions, green (validated on every commit of the series).
• ./vendor/bin/phpstan analyze --memory-limit=512M — level 10, no errors on every commit.