fix(reasoning): add Moonshot/Kimi to reasoning-content provider and model support (#3016)

Two targeted fixes to close the Kimi/Moonshot reasoning gap:

1. chat.rs: add ApiProvider::Moonshot to provider_accepts_reasoning_content
   so Kimi thinking traces stream as Thinking blocks instead of leaking
   as plain answer text on Moonshot's native endpoint.

2. models.rs: add kimi-* prefix match to model_supports_reasoning so
   bare Moonshot-native IDs (kimi-k2.6, kimi-*-thinking, etc.) are
   recognized as reasoning-capable without requiring the OpenRouter-style
   moonshotai/ prefix.

These two changes together ensure is_reasoning_model_for_stream returns
true for Kimi models on Moonshot, fixing the RC dialet gap.

crates/tui/src/client/chat.rs

@@ -1996,6 +1996,7 @@ fn provider_accepts_reasoning_content(provider: ApiProvider) -> bool {
             | ApiProvider::Volcengine
             | ApiProvider::Arcee
             | ApiProvider::Sglang
+            | ApiProvider::Moonshot // #3016: Kimi thinking traces use reasoning_content
     )
 }
 

crates/tui/src/models.rs

@@ -312,6 +312,10 @@ pub fn model_supports_reasoning(model: &str) -> bool {
     if lower.contains("deepseek") && lower.contains("v4") {
         return true;
     }
+    // #3016: Moonshot-native Kimi IDs also emit reasoning_content
+    if lower.starts_with("kimi-") {
+        return true;
+    }
     matches!(
         lower.as_str(),
         "arcee-ai/trinity-large-thinking"