Add theme-aware plugin icons

[Endless-Lemniscate]

What changed

• add a warm-white directory mark for dark mode
• replace the composer icon's nested tile with the transparent botnest mark
• add a matching dark-mode composer mark
• document the four portal asset mappings and bump the package to 1.0.2
• update the public support URL to the repository issue tracker

Why

The light artwork was reused in dark mode, making the black directory mark nearly invisible. The composer asset also contained its own rounded tile, producing a visually heavy icon-inside-an-icon treatment in ChatGPT.

Validation

• visually checked all four assets on white and #212121 backgrounds
• confirmed directory assets are 512×512 RGBA PNGs
• confirmed composer assets are 128×128 RGBA PNGs
• all 10 plugin tests pass
• deterministic 1.0.2 package builds successfully
• git diff --check passes