Fix docs layout, theme, and favicon

[aryamantodkar]

Summary

• Exclude the separate website/ site from Mintlify's documentation build. Its global CSS was being injected into the docs, capping main at 752 px and applying the website's dark background even when the docs switched to light mode.
• Set the docs favicon to the existing /premove-icon.png asset. The previously generated favicon URL returned 403.
• Keep the icon's original colors in light mode and invert only the navbar icon in dark mode.

Invariant

The root website and Mintlify docs own separate styles. The docs must not load the website stylesheet. This lets Mintlify size its center column around the navigation and table of contents, and lets its theme colors control the page background.

Without the .mintignore entry, desktop article text is about 305 px wide at a 1280 px viewport, and the base route shows dark backgrounds with dark text after switching to light mode.

Validation

• uv run --locked python scripts/agent/check.py focused --pytest tests/test_docs_routes.py — passed.
• git diff --check — passed.
• Local Mintlify preview: checked article widths from 320 px to 2048 px with no horizontal overflow. The article is about 529 px wide at 1280 px and 721 px at 2048 px.
• Toggled the base route between light and dark mode in the local preview; both states have readable backgrounds and text.
• Confirmed the generated local favicon returns HTTP 200 as image/png.