docs: add Spanish (LATAM) translation — README.es.md

[365diascollaboration-prog]

What this adds

README.es.md — a complete Spanish (Latin American) translation of the full README.

Translation decisions

• Tone preserved — the dry, confident personality of the original carries over. "No dice nada. Escribe una línea. Funciona." reads in Spanish the same way it lands in English.
• Technical terms untouched — ponytail: comments, command names (/ponytail-review, etc.), file paths, and CLI commands stay in English as developers will encounter them.
• LATAM neutral Spanish — no regional slang, readable across Mexico, Argentina, Colombia, Chile, Puerto Rico, and the rest of the Spanish-speaking world.
• All sections included — before/after, numbers, how it works, full install guide for every supported agent (Claude Code, Codex, Copilot CLI, Pi, OpenCode, Gemini, Antigravity, OpenClaw, Cursor, Windsurf, Cline, Kiro), commands table, development notes, FAQ, and license.

Why

Spanish is the second most-spoken language among developers worldwide. Latin America has one of the fastest-growing developer communities. A translated README removes the only barrier between ponytail and ~500M Spanish speakers who could use it today.