Keep model reasoning out of inserted polish text

Thinking-capable OpenAI-compatible models can return tagged reasoning before the final polished answer. The cleanup layer now strips only explicit think-tag blocks after response parsing so existing provider requests, UI, and fallback behavior stay unchanged.

Constraint: Issue #25 asks to adapt thinking output rather than disabling model thinking.

Rejected: Add a provider-specific thinking toggle | broader UI and settings change than needed for the bug.

Rejected: Strip localized heading text | too likely to remove normal user-facing content without a stable provider contract.

Confidence: medium

Scope-risk: narrow

Tested: cargo test polish::tests -- --nocapture

Tested: cargo check

openless-all/app/src-tauri/src/polish.rs

@@ -223,7 +223,8 @@ fn extract_assistant_content(body: &str) -> Result<String, LLMError> {
 /// an iterative trim — if the model stacks two boilerplate sentences we'll still
 /// strip both.
 fn clean_polish_output(content: &str) -> String {
-    let trimmed = content.trim();
+    let without_thinking = strip_thinking_blocks(content);
+    let trimmed = without_thinking.trim();
     let stripped = strip_markdown_fence(trimmed);
     let mut output = stripped.to_string();
 
@@ -239,6 +240,26 @@ fn clean_polish_output(content: &str) -> String {
     output.trim().to_string()
 }
 
+/// Strip model reasoning blocks so only the final polished text is inserted.
+///
+/// Thinking-capable OpenAI-compatible models commonly return their reasoning in
+/// `<think>...</think>` before the final answer, so keep this as a
+/// conservative cleanup layer after parsing `message.content` instead of
+/// provider-specific handling.
+fn strip_thinking_blocks(text: &str) -> String {
+    let mut output = text.to_string();
+
+    while let Some(start) = output.find("<think>") {
+        let Some(end_from_start) = output[start..].find("</think>") else {
+            break;
+        };
+        let end = start + end_from_start + "</think>".len();
+        output.replace_range(start..end, "");
+    }
+
+    output
+}
+
 fn strip_markdown_fence(text: &str) -> &str {
     if !(text.starts_with("```") && text.ends_with("```")) {
         return text;
@@ -348,3 +369,16 @@ pub mod prompts {
         )
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn clean_polish_output_strips_think_tag_block() {
+        let content =
+            "<think>先分析用户意图。\n这里可能很长。</think>\n\n请明天上午十点提醒我开会。";
+
+        assert_eq!(clean_polish_output(content), "请明天上午十点提醒我开会。");
+    }
+}