Release polished mascot icon

[enuzzo]

What changed

• replaces the accumulated mascot artwork with the approved clean ImageGen regeneration
• ships matching 128 px and 256 px WordPress.org icons
• uses the new runtime icon in the existing Settings → Sesamo header
• releases the visual update as version 0.2.1
• documents the sandboxed gh auth status fallback in AGENTS.md

Why

The previous icon had accumulated texture and detail through iterative edits. This regeneration restores crisp silhouettes, oversized readable ↑ ↓ B A keycaps, and a simpler thumbnail-safe composition.

Validation

• npm test
• ./scripts/build-release.sh
• unzip -t build/sesamo-v0.2.1.zip
• SHA-256 verification (10bb786b9dda2a42517ffb3285c5b3d9ba00e265729c21edbd59050d45f55462)
• WordPress 7.0.4 settings UI at 1536 px, 600 px, and 320 CSS px equivalent reflow
• official Plugin Check run against the exact runtime staging; pre-existing i18n findings remain outside this icon-only patch and WordPress.org publication remains gated