feat(cli): use external editor for commit message editing

index.ts

@@ -1,6 +1,9 @@
 #!/usr/bin/env bun
 
 import * as readline from "node:readline";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { unlink } from "node:fs/promises";
 import { loadConfig, saveConfig } from "./src/config";
 import {
   isGitRepo,
@@ -105,10 +108,38 @@ async function confirmCommit(message: string): Promise<"y" | "n" | "e"> {
 }
 
 async function editMessage(current: string): Promise<string | null> {
-  console.log(`  Current: ${DIM}${current}${RESET}`);
-  console.log(`  Enter new message (empty to abort):`);
-  const newMsg = await ask("  > ");
-  return newMsg || null;
+  const tmpPath = join(tmpdir(), `gai-msg-${Date.now()}`);
+
+  const header = `# Edit commit message below. Save and close to confirm.\n# Delete all lines to abort.\n`;
+  await Bun.write(tmpPath, header + current);
+
+  const editor =
+    process.env.VISUAL ||
+    process.env.EDITOR ||
+    (process.platform === "darwin" ? "vi" : "nano");
+
+  const proc = Bun.spawn([editor, tmpPath], {
+    stdout: "inherit",
+    stderr: "inherit",
+    stdin: "inherit",
+  });
+
+  const exitCode = await proc.exited;
+  if (exitCode !== 0) {
+    await unlink(tmpPath).catch(() => {});
+    return null;
+  }
+
+  const content = await Bun.file(tmpPath).text();
+  await unlink(tmpPath).catch(() => {});
+
+  const lines = content
+    .split("\n")
+    .filter((line) => !line.startsWith("#"))
+    .join("\n")
+    .trim();
+
+  return lines || null;
 }
 
 async function main() {