feat: enhance systemd unit and install script for browser dependencies

Updated the systemd unit generation to include the virtual environment and node modules in the PATH, improving the execution context for the hermes CLI. Additionally, added support for installing Playwright and its dependencies on Arch/Manjaro systems in the install script, ensuring a smoother setup process for browser tools.

tools/browser_tool.py

@@ -815,6 +815,13 @@ def _run_browser_command(
             level = logging.WARNING if result.returncode != 0 else logging.DEBUG
             logger.log(level, "browser '%s' stderr: %s", command, result.stderr.strip()[:500])
         
+        # Log empty output as warning — common sign of broken agent-browser
+        if not result.stdout.strip() and result.returncode == 0:
+            logger.warning("browser '%s' returned empty stdout with rc=0. "
+                           "cmd=%s stderr=%s",
+                           command, " ".join(cmd_parts[:4]) + "...",
+                           (result.stderr or "")[:200])
+
         # Parse JSON output
         if result.stdout.strip():
             try: