Update configuration and environment probing for improved flexibility and compatibility

- Modified the `load_config` function to allow launch preferences in `gpu-rent.vars` to override `.env` settings for non-secret variables, enhancing user control.
- Updated the list of Python candidates in `stack_env_probe.py` to include additional paths for ComfyUI, improving the detection of Python environments.
- Added new pip candidates in `tune_swarm_perf.py` to support various ComfyUI installations, ensuring better compatibility with different setups.

src/gpu_rent/remote/stack_env_probe.py

@@ -9,7 +9,14 @@ import subprocess
 import sys
 from pathlib import Path
 
-COMFY_PIPS = [
+DATA = Path("/mnt/swarm_data")
+# SwarmUI Linux: dlbackend/ComfyUI/venv (see comfy-install-linux.sh).
+# Older/alternate layouts kept as fallbacks; dlbackend lives on the data volume.
+COMFY_PYTHON_CANDIDATES = [
+    DATA / "dlbackend" / "ComfyUI" / "venv" / "bin" / "python",
+    DATA / "dlbackend" / "comfy" / "venv" / "bin" / "python",
+    DATA / "dlbackend" / "comfy" / "ComfyUI" / "venv" / "bin" / "python",
+    Path("/opt/swarmui/dlbackend/ComfyUI/venv/bin/python"),
     Path("/opt/swarmui/dlbackend/comfy/venv/bin/python"),
     Path("/opt/swarmui/dlbackend/comfy/ComfyUI/venv/bin/python"),
 ]
@@ -60,7 +67,14 @@ def check_cuda_runtime() -> dict:
 
 
 def find_comfy_python() -> Path | None:
-    for p in COMFY_PIPS:
+    for p in COMFY_PYTHON_CANDIDATES:
+        if p.is_file() and os.access(p, os.X_OK):
+            return p
+    # SwarmUI may nest differently under dlbackend/
+    for p in sorted(DATA.glob("dlbackend/**/venv/bin/python")):
+        if p.is_file() and os.access(p, os.X_OK):
+            return p
+    for p in sorted(Path("/opt/swarmui").glob("dlbackend/**/venv/bin/python")):
         if p.is_file() and os.access(p, os.X_OK):
             return p
     return None

src/gpu_rent/remote/tune_swarm_perf.py

@@ -19,8 +19,10 @@ GPU_JSON = DATA / ".gpu-rent-gpu.json"
 MARKER = DATA / ".gpu-rent-perf-tuned"
 BACKENDS = DATA / "Data" / "Backends.fds"
 COMFY_VENV_CANDIDATES = [
+    DATA / "dlbackend" / "ComfyUI" / "venv" / "bin" / "pip",
     DATA / "dlbackend" / "comfy" / "venv" / "bin" / "pip",
     DATA / "dlbackend" / "comfy" / "ComfyUI" / "venv" / "bin" / "pip",
+    Path("/opt/swarmui/dlbackend/ComfyUI/venv/bin/pip"),
     Path("/opt/swarmui/dlbackend/comfy/venv/bin/pip"),
     Path("/opt/swarmui/dlbackend/comfy/ComfyUI/venv/bin/pip"),
 ]