feat(backend): catalogue de providers OpenCode dynamique + provider personnalisé (#92)

Le catalogue de providers OpenCode lit désormais le cache local
~/.cache/opencode/models.json pour refléter les providers réellement
disponibles, avec repli garanti sur le catalogue statique en cas
d'absence ou d'erreur de lecture du cache. Ajout d'un champ additif
`custom` sur OpenCodeProviderConfig pour permettre à l'utilisateur de
déclarer un provider hors catalogue (id + clé API en saisie libre).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

crates/infrastructure/src/assistant/mod.rs

@@ -436,15 +436,28 @@ fn opencode_provider_config_json(
         "model".to_owned(),
         Value::String(format!("{}/{}", config.provider_id, config.model)),
     );
+    let mut options = Map::new();
+    options.insert("apiKey".to_owned(), Value::String(api_key.to_owned()));
+    let mut provider_entry = Map::new();
+    if let Some(custom) = config.custom.as_ref() {
+        // Provider outside the OpenCode registry: it needs the AI SDK package
+        // (`npm`), the endpoint (`options.baseURL`), and a `models` block —
+        // OpenCode has no built-in knowledge of this provider otherwise.
+        options.insert("baseURL".to_owned(), Value::String(custom.base_url.clone()));
+        provider_entry.insert("npm".to_owned(), Value::String(custom.npm.clone()));
+        let model_label = custom
+            .display_name
+            .clone()
+            .unwrap_or_else(|| config.model.clone());
+        provider_entry.insert(
+            "models".to_owned(),
+            json!({ config.model.as_str(): { "name": model_label } }),
+        );
+    }
+    provider_entry.insert("options".to_owned(), Value::Object(options));
     root.insert(
         "provider".to_owned(),
-        json!({
-            config.provider_id.as_str(): {
-                "options": {
-                    "apiKey": api_key
-                }
-            }
-        }),
+        json!({ config.provider_id.as_str(): provider_entry }),
     );
 
     let (command, args) = match runtime {
@@ -594,3 +607,69 @@ fn parent_dir(base: &ProjectPath, rel: &str) -> String {
         _ => base.as_str().trim_end_matches(['/', '\\']).to_owned(),
     }
 }
+
+#[cfg(test)]
+mod opencode_provider_config_json_tests {
+    use domain::profile::CustomProviderConfig;
+    use domain::ports::SecretRef;
+
+    use super::*;
+
+    fn known_provider_config() -> OpenCodeProviderConfig {
+        OpenCodeProviderConfig::new(
+            "anthropic",
+            "claude-sonnet-5",
+            SecretRef::new("secret-ref"),
+        )
+        .unwrap()
+    }
+
+    fn custom_provider_config() -> OpenCodeProviderConfig {
+        let custom =
+            CustomProviderConfig::new("@ai-sdk/openai-compatible", "https://my-endpoint/v1", None)
+                .unwrap();
+        OpenCodeProviderConfig::new("my-custom", "my-model", SecretRef::new("secret-ref"))
+            .unwrap()
+            .with_custom(custom)
+    }
+
+    #[test]
+    fn known_provider_emits_only_the_api_key_option() {
+        let config = known_provider_config();
+        let body = opencode_provider_config_json(&config, "sk-live", "/project", None);
+        let provider = &body["provider"]["anthropic"];
+        assert_eq!(provider["options"]["apiKey"], "sk-live");
+        assert!(provider["options"].get("baseURL").is_none());
+        assert!(provider.get("npm").is_none());
+        assert!(provider.get("models").is_none());
+    }
+
+    #[test]
+    fn custom_provider_emits_npm_base_url_and_models() {
+        let config = custom_provider_config();
+        let body = opencode_provider_config_json(&config, "sk-live", "/project", None);
+        let provider = &body["provider"]["my-custom"];
+        assert_eq!(provider["options"]["apiKey"], "sk-live");
+        assert_eq!(provider["options"]["baseURL"], "https://my-endpoint/v1");
+        assert_eq!(provider["npm"], "@ai-sdk/openai-compatible");
+        assert_eq!(provider["models"]["my-model"]["name"], "my-model");
+    }
+
+    #[test]
+    fn custom_provider_model_name_prefers_display_name() {
+        let custom = CustomProviderConfig::new(
+            "@ai-sdk/openai-compatible",
+            "https://my-endpoint/v1",
+            Some("My Model".to_owned()),
+        )
+        .unwrap();
+        let config = OpenCodeProviderConfig::new("my-custom", "my-model", SecretRef::new("ref"))
+            .unwrap()
+            .with_custom(custom);
+        let body = opencode_provider_config_json(&config, "sk-live", "/project", None);
+        assert_eq!(
+            body["provider"]["my-custom"]["models"]["my-model"]["name"],
+            "My Model"
+        );
+    }
+}