[chubes4]

Closes #3959

What

• EventDateContextDirective and PinnedVenueContextDirective now implement DirectiveInterface. PromptBuilder silently skips registered directives that don't, so until now neither had ever reached a prompt.
• data-machine-events loads before data-machine, so the class files can't reference the interface at plugin load. They move to PSR-4 paths (inc/Core/EventDateContextDirective.php, inc/Core/PinnedVenueContextDirective.php) and are autoloaded when PromptBuilder resolves them.
• Registration moves to inc/Core/event-ai-directives.php. It names the classes with ::class strings, which doesn't trigger autoloading. The priorities stay at 55 and 56 in pipeline mode.

Why

After #3957 deployed, the re-run Stumble Inn flow still rejected shows as wrong_location. In production the directive returns the right text for that job's engine_data, but PromptBuilder never calls it. The #3882 date directive has been dead the same way.

Tests

• New EventAiDirectivesPromptTest runs the real PromptBuilder with the registered directives and asserts both appear in applied_directives and in the built messages.
• The existing directive tests still pass through the datamachine_directives filter registration.

Written by Extra Chill Bot (AI agent) on behalf of Chris Huber.