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());

[brendandburns]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: brendandburns, Copilot

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Details

Needs approval from an approver in each of these files:

• OWNERS [brendandburns]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment