fix(deps): fetch electron binary via @electron/get, drop ^41 pin

The hotfix in #586 pinned electron to ^41 because electron@42.0.0
removed the postinstall that fetches the prebuilt binary into
node_modules/electron/dist/. That left us tethered to electron 41.x
and would re-break whenever 41 ages out of npm or the upstream
behavior shifts again.

This change does the binary fetch ourselves so we no longer depend on
electron's postinstall:

* New scripts/setup/fetch-electron-binary.js uses @electron/get to
  download the matching prebuilt binary for the host platform/arch
  and extract-zip to unpack it into dist/. Reads the version from
  the installed electron's package.json so it always matches what
  npm resolved.
* setup_electron_asar runs the helper only when npm install leaves
  dist/ missing. If electron later restores the postinstall, this
  is a no-op.
* Drops the 'electron@^41' pin so we follow latest electron again.
* @electron/get honors ELECTRON_MIRROR / ELECTRON_CACHE, so users
  behind proxies/mirrors keep working without further changes.

Refs #584

Co-Authored-By: Claude <claude@anthropic.com>

scripts/setup/dependencies.sh

@@ -215,16 +215,25 @@ setup_electron_asar() {
 
 	if [[ $install_needed == true ]]; then
 		echo "Installing Electron and Asar locally into $work_dir..."
-		# Pin to electron 41.x: electron@42.0.0 (2026-05-06) dropped the
-		# postinstall that fetches the prebuilt binary into dist/, leaving
-		# node_modules/electron/dist absent and the build aborting (#584).
-		# A durable fix using @electron/get is tracked separately.
-		if ! npm install --no-save 'electron@^41' @electron/asar; then
+		if ! npm install --no-save \
+			electron @electron/asar @electron/get extract-zip; then
 			echo 'Failed to install Electron and/or Asar locally.' >&2
 			cd "$project_root" || exit 1
 			exit 1
 		fi
 		echo 'Electron and Asar installation command finished.'
+
+		# electron@42+ no longer ships a postinstall script that fetches
+		# the prebuilt binary into dist/. If npm didn't populate it, fetch
+		# the matching binary explicitly via @electron/get. See #584.
+		if [[ ! -d $electron_dist_path ]]; then
+			echo 'Electron postinstall did not populate dist/; fetching binary explicitly...'
+			if ! node "$project_root/scripts/setup/fetch-electron-binary.js"; then
+				echo 'Failed to fetch Electron binary via @electron/get.' >&2
+				cd "$project_root" || exit 1
+				exit 1
+			fi
+		fi
 	else
 		echo 'Local Electron distribution and Asar binary already present.'
 	fi

scripts/setup/fetch-electron-binary.js

@@ -0,0 +1,69 @@
+#!/usr/bin/env node
+// Fetches the Electron prebuilt binary into node_modules/electron/dist/.
+//
+// electron@42.0.0 (2026-05-06) removed the postinstall script that
+// historically populated dist/ during `npm install`. This helper restores
+// that behavior using @electron/get + extract-zip, so the rest of the
+// build pipeline (which depends on the dist/ layout) keeps working.
+//
+// Run from the directory containing node_modules/electron. Reads the
+// installed electron version from its package.json and downloads the
+// matching binary for the host platform/arch.
+//
+// See: https://github.com/aaddrick/claude-desktop-debian/issues/584
+
+'use strict';
+
+const fs = require('node:fs');
+const path = require('node:path');
+
+async function main() {
+	const cwd = process.cwd();
+	const electronModuleDir = path.join(cwd, 'node_modules', 'electron');
+	const distDir = path.join(electronModuleDir, 'dist');
+
+	if (!fs.existsSync(electronModuleDir)) {
+		throw new Error(
+			`Electron module not found at ${electronModuleDir}; ` +
+			"run 'npm install electron' first.",
+		);
+	}
+
+	const pkgPath = path.join(electronModuleDir, 'package.json');
+	const { version } = JSON.parse(fs.readFileSync(pkgPath, 'utf8'));
+	if (!version) {
+		throw new Error(`Could not read version from ${pkgPath}`);
+	}
+
+	const platform = 'linux';
+	// node's process.arch values map cleanly to electron release archs,
+	// except 'arm' which electron publishes as 'armv7l'.
+	const arch = process.arch === 'arm' ? 'armv7l' : process.arch;
+
+	const { downloadArtifact } = require('@electron/get');
+	const extractZip = require('extract-zip');
+
+	console.log(`Fetching electron@${version} for ${platform}-${arch}...`);
+	const zipPath = await downloadArtifact({
+		version,
+		platform,
+		arch,
+		artifactName: 'electron',
+	});
+
+	console.log(`Extracting ${zipPath} into ${distDir}`);
+	fs.mkdirSync(distDir, { recursive: true });
+	await extractZip(zipPath, { dir: distDir });
+
+	const electronBin = path.join(distDir, 'electron');
+	if (fs.existsSync(electronBin)) {
+		fs.chmodSync(electronBin, 0o755);
+	}
+
+	console.log('Electron binary fetched and extracted successfully.');
+}
+
+main().catch((err) => {
+	console.error(err && err.stack ? err.stack : err);
+	process.exit(1);
+});