Add unit tests for DirectiveExecutor

[philippe-ths]

Parent

Part of #34

Goal

Verify that each directive type is dispatched and executed correctly.

What to test

• Each of the 13 directive types triggers the expected behavior
• Unknown directives are handled gracefully
• Interaction with movement, conversation, goal, sleep, tool, and function directives
• Error cases (e.g., invalid targets, missing prerequisites)

[philippe-ths]

Tracked but deferred — leaving open for future work.