feat: validate manifest version during pack command

Add validation to ensure the manifest_version matches the current expected
version (0.2) during the mcpb pack command. This prevents users from
packing extensions with outdated or incorrect manifest versions.

Changes:
- Add CURRENT_MANIFEST_VERSION constant to centralize version management
- Validate manifest version in pack command before creating bundle
- Update init command to use version constant
- Update tests to use version constant
- Fix prettier formatting issues

test/cli.test.ts

@@ -2,6 +2,8 @@ import { execSync } from "node:child_process";
 import fs from "node:fs";
 import { join } from "node:path";
 
+import { CURRENT_MANIFEST_VERSION } from "../src/schemas.js";
+
 interface ExecSyncError extends Error {
   stdout: Buffer;
   stderr: Buffer;
@@ -91,7 +93,7 @@ describe("DXT CLI", () => {
       fs.writeFileSync(
         join(tempDir, "manifest.json"),
         JSON.stringify({
-          manifest_version: "1.0",
+          manifest_version: CURRENT_MANIFEST_VERSION,
           name: "Test Extension",
           version: "1.0.0",
           description: "A test extension",
@@ -188,7 +190,7 @@ describe("DXT CLI", () => {
         fs.writeFileSync(
           join(tempExecDir, "manifest.json"),
           JSON.stringify({
-            manifest_version: "1.0",
+            manifest_version: CURRENT_MANIFEST_VERSION,
             name: "Test Executable Extension",
             version: "1.0.0",
             description: "A test extension with executable files",