disable Electron sandbox in npm run dev on Linux

Linux ships chrome-sandbox without SUID and AppArmor blocks the
namespace sandbox by default on Ubuntu 24.04+, so dev mode fails
without manual `chown root:root` + `chmod 4755` per worktree's
node_modules. Set ELECTRON_DISABLE_SANDBOX=1 in the dev scripts so
fresh worktrees just work. No effect on packaged builds.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: frenchie4111

package.json

@@ -9,8 +9,8 @@
   "license": "MIT",
   "description": "Harness - manage multiple Claude Code instances across git worktrees",
   "scripts": {
-    "dev": "electron-vite dev",
-    "dev:debug": "sh -c 'trap \"kill 0\" EXIT; tail -F \"$HOME/Library/Application Support/Harness (Dev)/debug.log\" & electron-vite dev'",
+    "dev": "ELECTRON_DISABLE_SANDBOX=1 electron-vite dev",
+    "dev:debug": "sh -c 'trap \"kill 0\" EXIT; tail -F \"$HOME/Library/Application Support/Harness (Dev)/debug.log\" & ELECTRON_DISABLE_SANDBOX=1 electron-vite dev'",
     "log": "tail -f ~/Library/Application\\ Support/harness/debug.log",
     "log:clear": "rm -f ~/Library/Application\\ Support/harness/debug.log",
     "log:perf": "tail -f ~/Library/Application\\ Support/harness/perf.log",