Texture the claude scenarios and respect the terminal palette

[namest504]

Summary

• claude scenarios now breathe like a real session: blank lines between turns, colored diff previews under Update calls (dim line numbers, red/green rows), and dim output dumps under Bash calls — three reworked scenarios showcase search, todo, and log-hunting flows
• body text everywhere now inherits the terminal's own palette: the shared typing renderer drops its hardcoded white-on-black, and five themes stop forcing white foregrounds — light-background terminals finally render legibly (matrix keeps its black world and HUD badges keep their explicit fg+bg pairs by design)
• a new contract test pins the no-forced-background rule for the typing renderer