feat(cli-tools): add Devin CLI provider with ACP stdio executor

Wire Devin CLI as a routed provider that spawns the local `devin acp`
binary. Add the DevinCliExecutor, register it in the executor map, expose
its status through the cli-tools batch endpoint and devin-settings route,
and document setup in cliTools constants.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/app/api/cli-tools/devin-settings/route.js

@@ -0,0 +1,78 @@
+"use server";
+
+import { NextResponse } from "next/server";
+import { exec } from "child_process";
+import { promisify } from "util";
+import fs from "fs/promises";
+import path from "path";
+import os from "os";
+
+const execAsync = promisify(exec);
+
+// Mirror the executor's resolveDevinBin discovery so the dashboard's status
+// matches what the runtime actually spawns.
+const candidateDevinPaths = () => {
+  const home = os.homedir();
+  const paths = [
+    path.join(home, ".local", "share", "devin", "bin", "devin"),
+    path.join(home, ".devin", "bin", "devin"),
+  ];
+  if (process.platform === "win32") {
+    const localAppData = process.env.LOCALAPPDATA || path.join(home, "AppData", "Local");
+    paths.push(path.join(localAppData, "devin", "cli", "bin", "devin.exe"));
+  }
+  return paths;
+};
+
+const checkDevinInstalled = async () => {
+  // 1. PATH lookup
+  try {
+    const isWindows = os.platform() === "win32";
+    const command = isWindows ? "where devin" : "which devin";
+    await execAsync(command, { windowsHide: true });
+    return { installed: true, source: "path" };
+  } catch {
+    // fall through to filesystem probes
+  }
+  // 2. Known installer paths
+  for (const candidate of candidateDevinPaths()) {
+    try {
+      await fs.access(candidate);
+      return { installed: true, source: candidate };
+    } catch { /* keep probing */ }
+  }
+  return { installed: false, source: null };
+};
+
+const readDevinVersion = async () => {
+  try {
+    const { stdout } = await execAsync("devin --version", { windowsHide: true });
+    return stdout.trim().split("\n")[0] || null;
+  } catch {
+    return null;
+  }
+};
+
+// GET — install detection only. No config to write: the binary handles its own auth.
+export async function GET() {
+  try {
+    const { installed, source } = await checkDevinInstalled();
+    if (!installed) {
+      return NextResponse.json({
+        installed: false,
+        message: "Devin CLI is not installed. Install it from https://cli.devin.ai and run `devin auth login`.",
+        installUrl: "https://cli.devin.ai",
+      });
+    }
+    const version = await readDevinVersion();
+    return NextResponse.json({
+      installed: true,
+      source,
+      version,
+      message: "Devin CLI detected. Make sure `devin auth login` has been run.",
+    });
+  } catch (error) {
+    console.log("Error checking devin settings:", error);
+    return NextResponse.json({ error: "Failed to check devin settings" }, { status: 500 });
+  }
+}