feat: label code fences so Vicinae can colour them (#10)

src/__tests__/markdown.test.ts

@@ -127,6 +127,25 @@ describe("buildThreadMarkdown", () => {
     expect(markdown).toContain("Ollama rejected the API key.");
   });
 
+  it("labels a bare code fence inside an answer", () => {
+    // Vicinae gives a dark panel, a language header and a Copy button
+    // (`MdCodeBlock.qml`); the label is what turns on syntax colouring.
+    const markdown = buildThreadMarkdown([
+      message({ role: "assistant", text: "Run this:\n\n```\ngit status\n```" }),
+    ]);
+
+    expect(markdown).toContain("```bash");
+  });
+
+  it("leaves a fence the model already labelled alone", () => {
+    const markdown = buildThreadMarkdown([
+      message({ role: "assistant", text: "```rust\nfn main() {}\n```" }),
+    ]);
+
+    expect(markdown).toContain("```rust");
+    expect(markdown).not.toContain("```bash");
+  });
+
   it("lists tools on one quiet line, flagging failures", () => {
     const markdown = buildThreadMarkdown([
       message({