v2: Add comprehensive tests for command DSL

[javiertoledo]

Parent

Part of #739

Context

The command DSL (command() function) currently has no direct unit tests. The decorator tests indirectly test it, but we need dedicated tests for:

1. DSL function tests (packages/core/test/dsl/command.test.ts):

   • Registration works correctly and metadata is stored in config
   • Duplicate name detection throws error
   • Default values (before defaults to [], methods defaults to [])
   • All three authorize option variants ('all', roles array, custom function)
   • Returned metadata matches what was registered
   • Properties are properly passed through
   • Handler function is stored correctly

2. DSL integration tests:

   • A command defined via command() can be dispatched through MagekCommandDispatcher
   • Authorization works for DSL-defined commands
   • Before hooks work for DSL-defined commands

3. Interoperability tests:

   • DSL commands and decorator commands can coexist in the same config
   • Both types are dispatched correctly

4. Decorator regression tests:

   • Ensure the existing decorator tests are comprehensive enough to catch regressions
   • The decorator's class instantiation adapter (Object.assign + handle) works correctly

Acceptance Criteria

• packages/core/test/dsl/command.test.ts created with comprehensive tests
• DSL and decorator tests are clearly separated
• All edge cases covered (no fields, no authorize, duplicate names, etc.)
• Integration test showing full dispatch flow with DSL-defined command