fix: increase API timeout from 3min to 5min

feat: switch to ZenMux API with OpenAI-compatible endpoint

feat: switch from OpenRouter to aicodemirror Gemini API

simplify: positional task arg, --html/--svg shorthands, auto-infer type, remove --task-file

skill: don't inject design opinions, let Gemini decide

simplify: trust Gemini to handle design decisions autonomously

balance: functional clarity + design freedom in prompts

improve: system prompts now require functional detail

feat: gemini-designer skill for design tasks via OpenRouter