Fix ModelMapper.processJarPackage breaking on paths containing '+'

[Copilot]

ModelMapper.processJarPackage used URLDecoder.decode to extract the JAR file path from a file: URL. URLDecoder follows application/x-www-form-urlencoded semantics where + → space, corrupting paths with literal + characters. This causes initModelMap() to fail silently, leaving the prebuilt model map empty. Manifests in Bazel 8 environments where canonical repo names use + (e.g., rules_jvm_external++maven+maven/...client-java-api-26.0.0.jar).

Changes

• Replace URLDecoder.decode with URI.create(...).getPath() for the file: JAR path case. URI.getPath() correctly decodes %XX sequences but treats + as a literal character — correct URL semantics.
• Remove raw packageURL.getFile() post-processing for jar:/nested: cases — these already went through JarURLConnection and were unaffected.
• Add guard for missing ! separator in the file: URL before calling substring.
• Remove now-unused imports URLDecoder and StandardCharsets.

// Before: + in path → converted to space → JarFile(...) fails
String jarFileName = URLDecoder.decode(packageURL.getFile(), StandardCharsets.UTF_8);
jarFileName = jarFileName.substring(5, jarFileName.indexOf("!"));
jf = new JarFile(jarFileName);

// After: + preserved, %20 still decoded correctly
int bangIndex = jarFileName.indexOf("!");
String filePart = jarFileName.substring(0, bangIndex);
jf = new JarFile(URI.create(filePart).getPath());

[k8s-ci-robot]

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