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/skills/spec-pipeline/SKILL.md

@@ -0,0 +1,23 @@
+---
+name: spec-pipeline
+description: "Lean implementation loop: Architect -> Developer -> User Verification."
+---
+
+## Execution Logic
+
+1. **Phase 1: Architecture (Optional for small edits)**
+   - `@architect` defines signatures, node structures, or spec updates in `specs/[feature-name].md`.
+   - **STOP:** Wait for user approval on design choices before invoking developer.
+
+2. **Phase 2: Implementation & Engine Validation**
+   - `@developer` updates code and scenes using targeted diffs/snippets.
+   - `@developer` runs headless syntax verification:
+     `& "C:\Godot4\Godot_v4.7.1-stable_win64_console.exe" --headless --check-only --script "res://path/to/script.gd" --path "C:\Godot4\project"`
+   - If static check fails, `@developer` fixes the code immediately.
+
+3. **Phase 3: User Hand-off (Stop)**
+   - Present the changes to the user to test inside the Godot Editor.
+   - Do NOT update READMEs or documentation yet.
+
+4. **Phase 4: Documentation (Triggered manually by user)**
+   - Only call `@writer` after the user confirms: _"Feature verified and working."_