EsbuildCompressor and minify.js silently fall back to uncompressed output

[bjagg]

Context

PR #303 introduced EsbuildCompressor.java (replacing YUI Compressor) and a build-time minify.js script. Both silently fall back to uncompressed output when esbuild is unavailable:

EsbuildCompressor.java:

} catch (IOException e) {
    logger.warn("esbuild not available, falling back to uncompressed output: " + e.getMessage());
}
// ...
try (FileReader fallbackReader = new FileReader(esbuildSucceeded ? outputFile.toFile() : inputFile.toFile())) {
    IOUtils.copy(fallbackReader, writer);
}

minify.js:

} catch (error) {
    console.warn(`Failed to minify ${file}: ${error.message}`);
    // Copy original file as fallback
    const minFile = file.replace(/\.js$/, '.min.js');
    fs.copyFileSync(file, minFile);
}

Problem

A deployment could ship a WAR with full-size .min.js files if esbuild fails or isn't on PATH. The only signal is a log warning, which is easy to miss in build output.

Proposed fix

• EsbuildCompressor.java: throw IOException when esbuild is unavailable or exits non-zero. Let the aggregator fail loud.
• minify.js: exit with non-zero on any minification failure. Do not create a .min.js that is actually full-size.
• If a build-time fallback is desirable (e.g., for dev-mode incremental builds), make it explicit via a Maven property or env var.

Priority

Low — the release can proceed without this fix. Filing as a follow-up to PR #303 so it doesn't block the 1.5.1 release.