ci: support scoped conventional commits in commit-message-check

[Copilot]

Summary

The commit-message-check CI workflow was rejecting valid conventional commit messages that include a scope, such as feat(cookie): prevent aggressive session cookie expiration.

Problem

The regex pattern only matched type: description format (e.g., feat: something) but did not support the widely-used scoped format type(scope): description (e.g., feat(cookie): something).

Changes

• Updated the regex pattern to optionally allow a scope in parentheses after the commit type: type(scope): description
• Used [^)]+ inside the scope group to reject empty scopes like feat(): message
• Separated merge/update patterns (which don't use a colon) into their own alternative for clarity
• Updated the error message to document the optional scope syntax with examples

Validation

Tested the new regex against:

• ✅ feat(cookie): prevent aggressive session cookie expiration
• ✅ feat: add new feature (no scope, still works)
• ✅ fix(auth): resolve login issue
• ✅ merge branch main
• ✅ All other existing commit types
• ❌ feat(): empty scope (correctly rejected)
• ❌ random commit message (correctly rejected)