Feature : Automatic version check and update notification for the product

[Foufou-exe]

Context

Currently, Spec Kit does not check if a new version of the CLI or product is available when launched. This can result in users running outdated versions without being notified.

Proposed Enhancement

• Add a feature that checks, at each launch or regularly, if the current version is the latest.
• If a new version is available, display a clear message to the user:

  "⚠️ A new version of Spec Kit is available! Update with: uv tool install specify-cli --force --from git+https://github.com/github/spec-kit.git"

• Provide a way to disable the check via an environment variable.
• Gracefully handle offline mode so usage isn't blocked if the user has no internet connection.
• Optionally, don't check too frequently (e.g., at most once per day).

Benefits

• Improves user experience
• Reduces risk of using an outdated version
• Encourages good update practices

Suggested labels

• enhancement
• in-agent-experience

Author: @Foufou-exe