Migrate Commet SDK v7 to v8

Use the v8 changelog as the detailed source of truth: https://commet.co/changelog/api-2026-07-24-and-sdks-v8

1. Detect the integration

Before editing, find:

• installed Commet packages and versions;
• every import, client initialization, SDK call, exported Commet type, direct REST request, and webhook handler;
• any explicit commet-version, API version pin, or webhook endpoint pin;
• the project's typecheck, build, and test commands.

Do not assume the project only uses Node. Check package.json, Python project files, go.mod, Gradle or Maven files, and composer.json.

2. Upgrade one major boundary