fix: REPL display, /compact panic, identity leak, DeepSeek reasoning, thinking blocks

Five interrelated fixes from parallel Hephaestus sessions:

1. fix(repl): display assistant text after spinner (#2981, #2982, #2937)
   - Added final_assistant_text() call after run_turn spinner completes
   - REPL now shows response text like run_prompt_json does

2. fix(compact): handle Thinking content blocks (#2985)
   - Added ContentBlock::Thinking variant throughout compact summarizer
   - Prevents panic when /compact encounters thinking blocks

3. fix(prompt): provider-aware model identity (#2822)
   - New ModelFamilyIdentity enum (Claude vs Generic)
   - Non-Anthropic models no longer say 'I am Claude'
   - model_family_identity_for() detects provider and sets identity

4. fix(openai): preserve DeepSeek reasoning_content (#2821)
   - Stream parser now captures reasoning_content from OpenAI-compat
   - Emits ThinkingDelta/SignatureDelta events for reasoning models
   - Thinking blocks included in conversation history for re-send

5. feat(runtime): Thinking block support across codebase
   - AssistantEvent::Thinking variant in conversation.rs
   - ContentBlock::Thinking in session serialization
   - Thinking-aware compact summarization
   - Tests for thinking block ordering and content

Closes #2981, #2982, #2937, #2985, #2822, #2821

rust/crates/api/tests/openai_compat_integration.rs

@@ -63,6 +63,50 @@ async fn send_message_uses_openai_compatible_endpoint_and_auth() {
     assert_eq!(body["tools"][0]["type"], json!("function"));
 }
 
+#[tokio::test]
+async fn send_message_preserves_deepseek_reasoning_content_before_text() {
+    let state = Arc::new(Mutex::new(Vec::<CapturedRequest>::new()));
+    let body = concat!(
+        "{",
+        "\"id\":\"chatcmpl_deepseek_reasoning\",",
+        "\"model\":\"deepseek-v4-pro\",",
+        "\"choices\":[{",
+        "\"message\":{\"role\":\"assistant\",\"reasoning_content\":\"Think first\",\"content\":\"Answer second\",\"tool_calls\":[]},",
+        "\"finish_reason\":\"stop\"",
+        "}],",
+        "\"usage\":{\"prompt_tokens\":11,\"completion_tokens\":5}",
+        "}"
+    );
+    let server = spawn_server(
+        state.clone(),
+        vec![http_response("200 OK", "application/json", body)],
+    )
+    .await;
+
+    let client = OpenAiCompatClient::new("openai-test-key", OpenAiCompatConfig::openai())
+        .with_base_url(server.base_url());
+    let response = client
+        .send_message(&MessageRequest {
+            model: "openai/deepseek-v4-pro".to_string(),
+            ..sample_request(false)
+        })
+        .await
+        .expect("request should succeed");
+
+    assert_eq!(
+        response.content,
+        vec![
+            OutputContentBlock::Thinking {
+                thinking: "Think first".to_string(),
+                signature: None,
+            },
+            OutputContentBlock::Text {
+                text: "Answer second".to_string(),
+            },
+        ]
+    );
+}
+
 #[tokio::test]
 async fn send_message_blocks_oversized_xai_requests_before_the_http_call() {
     let state = Arc::new(Mutex::new(Vec::<CapturedRequest>::new()));