Fix OOB in StaticResourcesProcessor for META-INF/resources-only JARs

1. 1. 1. What it does

This patch prevents a `StringIndexOutOfBoundsException` when a jar contains only the `META-INF/resources` entry (without any files underneath). Quarkus’ `StaticResourcesProcessor` was unconditionally calling:

```java
rel.substring(META_INF_RESOURCES.length())
```

even when `rel.equals("META-INF/resources")`, which triggers the out-of-bounds error.

1. 1. 1. How it’s fixed

We now guard on `rel.startsWith(prefix)` before stripping off the `META-INF/resources/` prefix:

```java
if (rel.startsWith(prefix))

{ String subPath = rel.substring(prefix.length()); knownPaths.add(new Entry(subPath, false)); }

```

This safely skips jars that don’t have any static files under `META-INF/resources`.

1. 1. 1. Issue

Closes #47666

1. 1. 1. Verification

I ran the graalpy-demo reproduction script in all modes (break, fix, and verify), and now the native build succeeds without error.

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Thank you for reviewing! 🙏