feat: refine fire demon face and torch-lit code wall

[ytvee]

Role and reference intent

Implemented as a senior creative technologist and real-time particle-animation engineer. The supplied references are treated as the source of truth for the eyes, mouth, fire behaviour and torch-lit background.

Summary

• rebuilds both eyes as slightly asymmetric layered graph structures with warm outer rims, dense cream/white annular particles, bright iris rings, radial iris-to-pupil spokes, compact black pupil hubs and small highlight clusters;
• adds subtle shared pupil gaze, independent sclera/iris twinkle and stronger highlight glow while keeping facial landmarks tightly anchored;
• rebuilds the smile from separate outer and inner upper/lower contours with reinforced corners, a sparse nearly black cavity, a dense lower tongue bed, a bright tongue arc and lip highlights;
• deepens the lower mouth silhouette in a presentation-graph pass and recalculates affected spring rest lengths;
• adds feature metadata so pupil, cavity, sclera, iris, highlights, tongue and lips can animate differently without increasing the two-draw-call rendering model;
• strengthens idle combustion with two travelling thermal bands, layered flicker, height-dependent turbulence, size breathing, dynamic per-node glow, edge pulses and rising embers;
• preserves full-section graph stretching with seven-step drag propagation and spring recovery;
• increases the background to eighteen dense code columns with 4.2–6px text, wall grain and scan-line texture;
• keeps the code below the WebGL canvas and reveals it only during drag through a speed-sensitive multi-stop radial mask, warm core and wall haze;
• sets torch variables on the graph surface itself so the illumination follows the pointer correctly;
• preserves static Astro HTML, lazy Three.js loading, adaptive density, SVG fallback, reduced-motion support and GPU cleanup.

Scope

Only the existing hero graph, code-wall background, focused tests and animation documentation are changed. No routes or additional sections are added.

Verification

GitHub Actions completed successfully:

• dependency installation — passed;
• graph determinism and structural tests — passed;
• detailed eye feature tests — passed;
• detailed mouth feature tests — passed;
• interaction physics tests — passed;
• Astro strict type checking — passed;
• production build — passed.

Closes #6