Phase 39: Provider Adapter Refactor

- ProviderAdapter trait with chat(), embed(), unload(), health()
- OllamaAdapter wrapping existing AiClient
- OpenRouterAdapter for openrouter.ai API integration
- provider_key() routing by model prefix (openrouter/*, etc)

crates/aibridge/src/providers/ollama.rs

@@ -0,0 +1,37 @@
+use async_trait::async_trait;
+use crate::client::{AiClient, GenerateRequest, GenerateResponse, EmbedRequest, EmbedResponse};
+use crate::provider::ProviderAdapter;
+
+pub struct OllamaAdapter {
+    client: AiClient,
+}
+
+impl OllamaAdapter {
+    pub fn new(client: AiClient) -> Self {
+        Self { client }
+    }
+}
+
+#[async_trait]
+impl ProviderAdapter for OllamaAdapter {
+    fn name(&self) -> &str {
+        "ollama"
+    }
+
+    async fn chat(&self, req: GenerateRequest) -> Result<GenerateResponse, String> {
+        self.client.generate(req).await
+    }
+
+    async fn embed(&self, req: EmbedRequest) -> Result<EmbedResponse, String> {
+        self.client.embed(req).await
+    }
+
+    async fn unload(&self, model: &str) -> Result<(), String> {
+        let _: serde_json::Value = self.client.unload_model(model).await?;
+        Ok(())
+    }
+
+    async fn health(&self) -> Result<serde_json::Value, String> {
+        self.client.health().await
+    }
+}