fix(probe): system-python capability check via ollama binary

The earlier fix probed 'openai' via import at the install.sh /
lem-eval.sh level, but those scripts run in the SYSTEM python outside
the uv venv where openai isn't installed. So charon correctly saw
mlx_lm as unavailable but then also failed the gguf probe and
reported 'no target types detected'.

Switch to a presence check: ollama binary in PATH → gguf capability.
That's the right proxy anyway — we run gguf via Ollama's OpenAI
endpoint, and if ollama isn't installed we can't run anyway.

mlx probe unchanged (only meaningful on Darwin).

Co-Authored-By: Virgil <virgil@lethean.io>

install.sh

@@ -67,19 +67,19 @@ if types_env:
     allowed = set(t.strip() for t in types_env.split(","))
 else:
     allowed = set()
-    try:
-        import mlx_lm  # noqa: F401
-        if platform.system() == "Darwin":
+    if platform.system() == "Darwin":
+        try:
+            import mlx_lm  # noqa: F401
             allowed.add("mlx")
-    except ImportError:
-        pass
-    try:
-        import openai  # noqa: F401
+        except ImportError:
+            pass
+    # gguf availability = ollama binary present anywhere we'd hit it from
+    if any(os.path.exists(os.path.join(p, "ollama"))
+           for p in os.environ.get("PATH", "").split(":")):
         allowed.add("gguf")
-    except ImportError:
-        pass
     if not allowed:
-        print("  no target types detected (need mlx_lm or openai); set LEM_TYPES=gguf to override")
+        print("  no target types detected (need mlx_lm on Darwin or ollama on PATH); "
+              "set LEM_TYPES to override")
 
 def derive_repo_id(this_ref):
     """Strip Ollama hf.co/ prefix and :<tag> suffix to get a clone-able repo id."""

lem-eval.sh

@@ -109,17 +109,15 @@ if types_env:
     allowed = set(t.strip() for t in types_env.split(","))
 else:
     allowed = set()
-    try:
-        import mlx_lm  # noqa: F401
-        if platform.system() == "Darwin":
+    if platform.system() == "Darwin":
+        try:
+            import mlx_lm  # noqa: F401
             allowed.add("mlx")
-    except ImportError:
-        pass
-    try:
-        import openai  # noqa: F401
+        except ImportError:
+            pass
+    if any(os.path.exists(os.path.join(p, "ollama"))
+           for p in os.environ.get("PATH", "").split(":")):
         allowed.add("gguf")
-    except ImportError:
-        pass
 
 def derive_repo_id(this_ref):
     if this_ref.startswith("hf.co/"):