fix: keep psutil optional for system health

requirements.txt

@@ -1,13 +1,14 @@
 # Hermes Web UI -- minimal Python dependencies
 # The server uses PyYAML plus cryptography for optional local passkey/WebAuthn support.
-# psutil is used only for safe aggregate cross-platform CPU/RAM metrics when
-# Linux procfs is unavailable (for example on macOS).
 # All heavy ML/agent deps live in the Hermes agent venv.
 #
 # OPTIONAL: the Edge TTS speech engine (Settings -> Voice -> TTS Engine -> "Edge TTS")
 # needs `edge-tts`. It is intentionally NOT a hard dependency — the /api/tts
 # endpoint returns 503 with an install hint when it's absent. Install it only if
 # you want server-side Microsoft neural voices:  pip install edge-tts
+#
+# OPTIONAL: macOS/non-procfs CPU/RAM system-health metrics need `psutil`.
+# Linux uses procfs without this dependency; install only if you want aggregate
+# CPU/RAM metrics on platforms without /proc:  pip install psutil>=5.9
 pyyaml>=6.0
 cryptography>=42.0
-psutil>=5.9