feat: Implement Phase 4 Trigger Events System

- Added a new event-driven system for reactive storytelling, allowing rules like "When X happens, do Y."
- Introduced TriggerArea class for placeable sensors in the stage.
- Enhanced StickmanRig to emit signals for actions and arrivals.
- Updated StageDirectorVisuals to render rules visually with labels and badges.
- Modified StageSpawner to support spawning TriggerAreas.
- Improved text baseline calculations in speech bubbles and rule labels.
- Added tests for text baseline fixes to ensure proper rendering.
- Documented the implementation plan for Phase 4 in PHASE_4_TRIGGER_EVENTS.md.
- Created a polish plan for Phase 4 in PHASE_4b_POLISH.md.

plans/PHASE_4b_POLISH.md

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+# Phase 4: Triggers & Event System — Implementation Plan
+
+## 1. Overview
+
+We have a good start with feature implementation, we want to polish some of the features and fix bugs before the next phase. We don't want too much tech debt
+
+## 2. UI