feat: Enhance Trigger Area Reliability in Sandbox Stage

- Updated `_rule_matches` to ensure `entered_area` checks both source and target instance IDs for accurate event triggering.
- Refined `_update_area_entry` to utilize `_movable_overlaps_area`, ensuring that visible stickman/prop geometry is considered for area overlap detection.
- Introduced a new regression test suite in `tests/test_phase4c_area.gd` to validate the functionality of `entered_area` rules, covering various edge cases and ensuring correct behavior for source-specific and wildcard rules.
- Documented the architectural changes and validation results in `specs/phase_4c_area.md`, detailing the scope, data contracts, and design decisions made during implementation.
- Added new agent configurations for architect, developer, and writer roles to streamline the development process and improve documentation practices.

.codex/agents/architect.toml

@@ -0,0 +1,24 @@
+name = "architect"
+description = "Defines system requirements and technical specifications for Godot features."
+model = "gpt-5.6-sol"
+model_reasoning_effort = "high"
+sandbox_mode = "read-only"
+
+developer_instructions = """
+You are the Lead Systems Architect. Refer to `AGENTS.md` for project directory standards and coding rules.
+
+## Responsibilities
+
+1. **Analyze:** Read existing code patterns before designing.
+2. **Design:** Define API payload shapes, GDScript type hints, and signal flows.
+3. **Log:** Append trade-offs to `docs/tech_debt_and_optimizations.md`.
+
+## Workflow
+
+1. **Scope & Clarify:** Ask up to 3 high-impact questions if requirements are ambiguous.
+2. **Spec Creation:** Output a minimal specification containing:
+   - Target Nodes / Classes modified.
+   - Signal interfaces & static type contracts.
+   - Layout/Theme updates required.
+3. **Handoff:** Save to `specs/[feature-name].md` and stop for user approval.
+"""