Use requested SSI plugin path in CLI

Author: chubes4

apps/cli/lib/dependency-management/paths.ts

@@ -58,8 +58,12 @@ export function getBlueprintsPharPath(): string {
 
 // Static Site Importer ships read-only with the CLI bundle (downloaded at npm
 // install time by `scripts/download-wp-server-files.ts`) and is symlinked into
-// each site's mu-plugins temp directory. No writable cache needed — the
-// bundled directory is treated as the source of truth.
+// each site's mu-plugins temp directory. Bench harnesses may override that
+// bundled copy to test an active SSI worktree.
 export function getStaticSiteImporterPluginPath(): string {
+	if ( process.env.STUDIO_STATIC_SITE_IMPORTER_PLUGIN_PATH ) {
+		return process.env.STUDIO_STATIC_SITE_IMPORTER_PLUGIN_PATH;
+	}
+
 	return path.join( getWpFilesPath(), 'static-site-importer' );
 }

apps/cli/lib/dependency-management/tests/paths.test.ts

@@ -0,0 +1,22 @@
+import path from 'path';
+import { afterEach, describe, expect, it } from 'vitest';
+import { getStaticSiteImporterPluginPath } from '../paths';
+
+describe( 'dependency path helpers', () => {
+	afterEach( () => {
+		delete process.env.STUDIO_STATIC_SITE_IMPORTER_PLUGIN_PATH;
+	} );
+
+	it( 'uses the requested Static Site Importer plugin path when provided', () => {
+		process.env.STUDIO_STATIC_SITE_IMPORTER_PLUGIN_PATH =
+			'/tmp/static-site-importer-worktree';
+
+		expect( getStaticSiteImporterPluginPath() ).toBe( '/tmp/static-site-importer-worktree' );
+	} );
+
+	it( 'falls back to the bundled Static Site Importer plugin path', () => {
+		expect( getStaticSiteImporterPluginPath() ).toContain(
+			path.join( 'wp-files', 'static-site-importer' )
+		);
+	} );
+} );