Revive ckitty as a polished unified terminal app

[fortunexbt]

Summary

• Rebuilt ckitty around one deterministic, dependency-free rendering core and one ckitty binary.
• Improved the ASCII silhouettes for sitting, sleeping, playing, and walking poses, including recognizable heads, bodies, paws, tails, toys, and birds.
• Added ASCII/NO_COLOR fallback, resize-safe terminal rendering, strict CLI validation, deterministic dump mode, live reveal, and portable timing.
• Added core, CLI/error, sanitizer, Linux/macOS CI, install, contributor, examples, and release documentation.
• Removed superseded v2/v3 sources and duplicate artifacts.

Visual verification

Ran the live app in macOS Terminal and captured plain-ASCII and color screenshots for fixed-seed poses. Verified that the cat silhouette remains readable, color roles separate fur/face/toys, and NO_COLOR=1 produces a clean monochrome fallback.

Validation

• make check
• make sanitize
• GCC build on macOS
• Temporary-prefix install/uninstall smoke test
• git diff --check