feat(core): add SourceResolver for backwards-compatible src/ → source/ migration

Introduces SourceResolver utility class with source/ → src/ → htdocs/
fallback chain, replacing hardcoded src/ references across 28 files.
This enables renaming root-level src/ to source/ in all repos while
maintaining backwards compatibility during the transition.

Phase 1: New lib/Enterprise/SourceResolver.php with resolve(),
resolveAbsolute(), globSource(), findUnderSource(), warnIfLegacy()
Phase 2: Updated 19 CLI/deploy tools to use SourceResolver
Phase 3: Updated 7 validator/lib files (McpServerPlugin,
PackageBuilder, RepositorySynchronizer, auto_detect_platform,
check_dolibarr_module, check_client_theme, check_structure)

Authored-by: Moko Consulting
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cli/updates_xml_build.php

@@ -17,7 +17,7 @@ declare(strict_types=1);
 
 require_once __DIR__ . '/../lib/Enterprise/CliFramework.php';
 
-use MokoEnterprise\CliFramework;
+use MokoEnterprise\{CliFramework, SourceResolver};
 
 class UpdatesXmlBuildCli extends CliFramework
 {
@@ -109,7 +109,7 @@ class UpdatesXmlBuildCli extends CliFramework
         // -- Locate Joomla manifest ---------------------------------------------------
         $manifest = null;
 
-        $candidates = glob("{$root}/src/pkg_*.xml") ?: [];
+        $candidates = SourceResolver::globSource($root, 'pkg_*.xml');
         foreach ($candidates as $f) {
             if (strpos(file_get_contents($f), '<extension') !== false) {
                 $manifest = $f;