Expanded the cost calculator — 14 models, 6 providers

Quick build update: the token-cost calculator I mentioned a few days ago now covers 14 models — GPT-5.6, Claude, Gemini, Grok, DeepSeek, and Perplexity. Enter your monthly token volume and see a sorted, real comparison.
Deliberately left out credit-based tools (Manus, Lovable, etc.) since they don't have per-token pricing and mixing them in would be misleading — those live in the main directory instead.