Add Charmtone Pantera SSH theme

[y0usaf]

I wanted to bring the Pantera palette over from Charmbracelet Crush as a small, focused theme PR.

What this adds

• a built-in pantera SSH theme (Charmtone Pantera in the picker)
• a semantic palette mapped from Crush's default Charmtone Pantera theme
• an inline source credit in theme.rs linking back to the upstream theme definition

Credit

This theme is based on Charmbracelet Crush's default theme:
https://github.com/charmbracelet/crush/blob/main/internal/ui/styles/themes.go

Notes

The original source is a 16-color palette, so this adapts it into late.sh's semantic theme slots while trying to preserve the same overall feel: dark base, vivid purple/teal accents, and bright yellow highlights.

Verification

• cargo fmt --all
• cargo check -p late-ssh (I couldn't complete this locally because of linker/jemalloc toolchain issues in this environment, so CI will need to do the final validation.)