feat: launch first-time setup in webui (#5078)

nanobot/providers/factory.py

@@ -212,6 +212,22 @@ def make_provider(
     return provider
 
 
+def build_unconfigured_provider_snapshot(config: Config, setup_error: str) -> ProviderSnapshot:
+    """Build a non-networking runtime so the WebUI can collect first-time setup."""
+    from nanobot.providers.unconfigured_provider import UnconfiguredProvider
+
+    preset = config.resolve_preset()
+    provider = UnconfiguredProvider(preset.model)
+    provider.generation = preset.to_generation_settings()
+    return ProviderSnapshot(
+        provider=provider,
+        model=preset.model,
+        context_window_tokens=preset.context_window_tokens,
+        signature=("unconfigured", setup_error, preset.model),
+        generation=provider.generation,
+    )
+
+
 def provider_signature(
     config: Config,
     *,

nanobot/providers/unconfigured_provider.py

@@ -0,0 +1,36 @@
+"""Provider used while the local WebUI is waiting for first-time setup."""
+
+from __future__ import annotations
+
+from nanobot.providers.base import LLMProvider, LLMResponse
+
+
+class UnconfiguredProvider(LLMProvider):
+    """Keep the gateway available for settings before a model is configured."""
+
+    def __init__(self, default_model: str) -> None:
+        super().__init__()
+        self._default_model = default_model
+
+    async def chat(
+        self,
+        messages: list[dict],
+        tools: list[dict] | None = None,
+        model: str | None = None,
+        max_tokens: int = 4096,
+        temperature: float = 0.7,
+        reasoning_effort: str | None = None,
+        tool_choice: str | dict | None = None,
+    ) -> LLMResponse:
+        return LLMResponse(
+            content=(
+                "Nanobot needs a model before it can chat. Open Settings → Models "
+                "to configure a provider and model, then send your message again."
+            ),
+            finish_reason="error",
+            error_kind="configuration",
+            error_should_retry=False,
+        )
+
+    def get_default_model(self) -> str:
+        return self._default_model