add testing module; integrate holographic effects into vial_fill shader with noise texture, sum-of-sines water surface, top-down lighting, foam line, and font outlines for readability

AGENTS.md

@@ -18,6 +18,15 @@ V Panel is a Godot Engine project that builds a fancy real-time status monitor.
 - Signals: past tense verb (e.g., `value_changed`, `panel_resized`).
 - Scene files: PascalCase matching their main script (e.g., `CpuPanel.tscn`).
 
+### Shaders
+- `vial_fill.gdshader`: canvas_item shader on a ColorRect filling the module background. Uses rounded-rect SDF (`rr_sdf`), sum-of-sines water surface with edge damping, and layered effects (wave distortion, ripple rings, swirl, HSV shift, top-down lighting, sparkle, foam line).
+- Noise texture: a static 100×100 PNG (`assets/textures/noise_100.png`) loaded at runtime and passed as `noise_tex` sampler2D uniform. Used for organic distortion modulation.
+- Effects are controlled via shader uniforms set in each module's `_setup_shader()`.
+
+### Labels / Readability
+- All percentage labels get a 3px black outline (`outline_size` / `font_outline_color`) for legibility against the liquid shader background.
+- Title labels get a 2px outline.
+
 ### Project Structure
 ```
 res://
@@ -31,7 +40,8 @@ res://
 │   ├── cpu/
 │   ├── memory/
 │   ├── network/
-│   └── disk/
+│   ├── disk/
+│   └── testing/
 ├── scenes/          # Root scenes (dashboard, etc.)
 ├── scripts/         # Shared utility scripts
 ├── themes/          # Theme definitions and style resources