Allow code generation with local models that require no API key

In local mode the OpenAI-compatible endpoint (Ollama, LM Studio, ...)
ignores auth, but two things blocked submitting a query without a key:
the Generate Code button was gated on a non-empty api_token, so it never
appeared, and the client refuses to construct an OpenAI client with an
empty key.

Show the button whenever a key is not required (local mode) or one is
present (cloud), and fall back to a placeholder key in local mode that a
real key typed into the field overrides. Cloud providers (OpenAI,
Anthropic, Gemini, NIM) still require a real key, so an empty key there
still surfaces the "Set API Key" prompt as before.

Author: jlee-kitware

src/vtk_prompt/state/config_state.py

@@ -11,9 +11,19 @@
 
 
 def get_api_key(app: Any) -> str | None:
-    """Get API key from state (requires manual input in UI)."""
+    """Get API key from state.
+
+    Cloud providers need a real key. Local models hit an OpenAI-compatible
+    endpoint (Ollama, LM Studio, ...) that ignores auth, but the OpenAI client
+    still refuses to construct with an empty key, so in local mode we fall back
+    to a placeholder. A real key typed into the field overrides it.
+    """
     api_token = getattr(app.state, "api_token", "")
-    return api_token.strip() if api_token and api_token.strip() else None
+    if api_token and api_token.strip():
+        return api_token.strip()
+    if not app.state.use_cloud_models:
+        return "sk-no-key-required"
+    return None
 
 
 def get_base_url(app: Any) -> str | None:

src/vtk_prompt/ui/layout/content.py

@@ -116,7 +116,7 @@ def build_content(layout: Any, app: Any) -> None:
                                 loading=("trame__busy", False),
                                 click=app.ctrl.generate_code,
                                 classes="my-2",
-                                v_show="api_token.trim()",
+                                v_show="!use_cloud_models || api_token.trim()",
                             )
                             vuetify.VBtn(
                                 "Set API Key",