[gr8man]

Description
In Autoloader::loadComposerNamespaces(), whenever Composer namespaces are loaded, the autoloader was unconditionally calling InstalledVersions::getAllRawData(), performing an array_merge across all installed package versions, and executing a triple-nested loop testing str_starts_with($path, $installPath) for every single PSR-4 namespace.

In almost all applications, Config\Modules::$composerPackages is empty (default configuration with neither only nor exclude specified). In this default state, all registered PSR-4 prefixes from Composer already belong to installed packages (or the root package) and can be registered directly into $this->prefixes without scanning InstalledVersions.

This PR adds a fast-path for the default configuration:

• Checks if $only === [] && $exclude === [] upfront.
• Directly registers the trimmed PSR-4 namespaces into $this->prefixes, skipping InstalledVersions::getAllRawData(), array_merge, and the triple-nested str_starts_with() matching loop entirely.
• When package filtering is configured (only or exclude), the original full validation logic is preserved with zero BC breaks.

Benchmark (10,000 iterations)

• Original loadComposerNamespaces(): 1496.44 ms (~0.150 ms per request)
• Fast-path loadComposerNamespaces(): 144.24 ms (~0.014 ms per request)
• Speedup: 10.4x (90.4% latency reduction during autoloader bootstrap)

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value (without duplication)
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide