feat(ai): strip MiniMax inline reasoning blocks

src/lib/ai/think-strip.test.ts

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+import { describe, it, expect } from "vitest";
+import { stripThinking } from "@/lib/ai/think-strip";
+
+describe("stripThinking", () => {
+  it("leaves ordinary text alone", () => {
+    expect(stripThinking("Fixed the quote form.")).toBe("Fixed the quote form.");
+  });
+
+  it("removes a think block and trims what is left", () => {
+    expect(
+      stripThinking("<think>Let me consider this.</think>\nFixed the quote form.")
+    ).toBe("Fixed the quote form.");
+  });
+
+  it("removes several blocks", () => {
+    expect(stripThinking("<think>a</think>One.<think>b</think>Two.")).toBe(
+      "One.Two."
+    );
+  });
+
+  it("handles a block spanning newlines", () => {
+    expect(stripThinking("<think>\nline one\nline two\n</think>Result.")).toBe(
+      "Result."
+    );
+  });
+
+  it("drops an unclosed block rather than showing it", () => {
+    // A truncated response can leave <think> open. Showing the reasoning is
+    // worse than showing nothing — the client sees the model talking to itself.
+    expect(stripThinking("Good.<think>Now let me reconsider")).toBe("Good.");
+  });
+
+  it("is case-insensitive about the tag", () => {
+    expect(stripThinking("<THINK>x</THINK>Done.")).toBe("Done.");
+  });
+
+  it("returns an empty string for content that is only thinking", () => {
+    expect(stripThinking("<think>all of it</think>")).toBe("");
+  });
+
+  it("handles empty input", () => {
+    expect(stripThinking("")).toBe("");
+  });
+});

src/lib/ai/think-strip.ts

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+/**
+ * Removes <think>...</think> reasoning from a MiniMax response.
+ *
+ * MiniMax M2.x emits its chain of thought inline in the normal content field.
+ * Anthropic returns reasoning as separate blocks, so this is a provider quirk
+ * and belongs to the OpenAI-compatible adapter alone. Left in, every commit
+ * summary a client reads would open with the model deliberating.
+ *
+ * Mega's equivalent handles a STREAM, where a tag can split across chunk
+ * boundaries ("<thi" + "nk>") and text must be held back. This phase does not
+ * stream, so the whole string is available and the simple form is correct.
+ */
+
+const THINK_BLOCK = /<think>[\s\S]*?<\/think>/gi;
+/** A response truncated mid-reasoning leaves an unclosed tag. */
+const UNCLOSED_THINK = /<think>[\s\S]*$/i;
+
+export function stripThinking(text: string): string {
+  return (text ?? "")
+    .replace(THINK_BLOCK, "")
+    .replace(UNCLOSED_THINK, "")
+    .trim();
+}