feat(HAI-076): add cross-compilation support for CLI executable builds

- Extend build.ts with cross-compilation targets for multiple platforms/architectures
- Add build:exe:all npm script to package.json for building all targets
- Add cross-compilation tests for build-exe-cross
- Add cross-compilation documentation section to README
- Clean up unused agent log, store, and route code across dashboard/core/engine packages

packages/cli/src/__tests__/build-exe-cross.test.ts

@@ -0,0 +1,134 @@
+import { describe, it, expect, beforeAll } from "vitest";
+import { execSync, spawnSync } from "node:child_process";
+import { existsSync, statSync } from "node:fs";
+import { join } from "node:path";
+
+const cliRoot = join(import.meta.dirname!, "..", "..");
+const distDir = join(cliRoot, "dist");
+const clientDir = join(distDir, "client");
+
+const SUPPORTED_TARGETS = [
+  "bun-linux-x64",
+  "bun-linux-arm64",
+  "bun-darwin-x64",
+  "bun-darwin-arm64",
+  "bun-windows-x64",
+] as const;
+
+/**
+ * Map target → expected binary filename (mirrors build.ts logic).
+ */
+function expectedBinaryName(target: string): string {
+  const suffix = target.replace(/^bun-/, "");
+  const isWindows = target.includes("windows");
+  return `hai-${suffix}${isWindows ? ".exe" : ""}`;
+}
+
+/**
+ * Determine the native target for the current host so we can run it.
+ */
+function nativeTarget(): string | null {
+  const platform = process.platform === "darwin" ? "darwin" : process.platform === "linux" ? "linux" : null;
+  const arch = process.arch === "x64" ? "x64" : process.arch === "arm64" ? "arm64" : null;
+  if (!platform || !arch) return null;
+  return `bun-${platform}-${arch}`;
+}
+
+describe("build-exe-cross: single target", () => {
+  beforeAll(() => {
+    // Build for linux-x64 specifically
+    execSync("bun run build.ts --target bun-linux-x64", {
+      cwd: cliRoot,
+      stdio: "pipe",
+      timeout: 120_000,
+    });
+  }, 180_000);
+
+  it("produces dist/hai-linux-x64", () => {
+    const bin = join(distDir, "hai-linux-x64");
+    expect(existsSync(bin)).toBe(true);
+    expect(statSync(bin).size).toBeGreaterThan(0);
+  });
+
+  it("copies client assets alongside the binary", () => {
+    expect(existsSync(join(clientDir, "index.html"))).toBe(true);
+  });
+});
+
+describe("build-exe-cross: windows target has .exe extension", () => {
+  beforeAll(() => {
+    execSync("bun run build.ts --target bun-windows-x64", {
+      cwd: cliRoot,
+      stdio: "pipe",
+      timeout: 120_000,
+    });
+  }, 180_000);
+
+  it("produces dist/hai-windows-x64.exe", () => {
+    const bin = join(distDir, "hai-windows-x64.exe");
+    expect(existsSync(bin)).toBe(true);
+    expect(statSync(bin).size).toBeGreaterThan(0);
+  });
+});
+
+describe("build-exe-cross: --all builds all platforms", () => {
+  beforeAll(() => {
+    execSync("bun run build.ts --all", {
+      cwd: cliRoot,
+      stdio: "pipe",
+      timeout: 300_000,
+    });
+  }, 360_000);
+
+  for (const target of SUPPORTED_TARGETS) {
+    const name = expectedBinaryName(target);
+    it(`produces dist/${name}`, () => {
+      const bin = join(distDir, name);
+      expect(existsSync(bin)).toBe(true);
+      expect(statSync(bin).size).toBeGreaterThan(0);
+    });
+  }
+
+  it("copies client assets", () => {
+    expect(existsSync(join(clientDir, "index.html"))).toBe(true);
+  });
+
+  it("native-platform binary runs --help", () => {
+    const target = nativeTarget();
+    if (!target) {
+      // Skip on unsupported host (e.g. Windows in CI)
+      return;
+    }
+    const name = expectedBinaryName(target);
+    const bin = join(distDir, name);
+    if (!existsSync(bin)) return;
+
+    const result = spawnSync(bin, ["--help"], {
+      encoding: "utf-8",
+      timeout: 15_000,
+    });
+    expect(result.status).toBe(0);
+    expect(result.stdout).toContain("hai");
+  });
+});
+
+describe("build-exe-cross: default (no args) backward compatibility", () => {
+  beforeAll(() => {
+    execSync("bun run build.ts", {
+      cwd: cliRoot,
+      stdio: "pipe",
+      timeout: 120_000,
+    });
+  }, 180_000);
+
+  it("produces dist/hai (no platform suffix)", () => {
+    const defaultName = process.platform === "win32" ? "hai.exe" : "hai";
+    const bin = join(distDir, defaultName);
+    expect(existsSync(bin)).toBe(true);
+    expect(statSync(bin).size).toBeGreaterThan(0);
+  });
+
+  it("copies client assets", () => {
+    expect(existsSync(join(clientDir, "index.html"))).toBe(true);
+  });
+});