Add Sysdig color scheme toggle (t key)

[ConorDSherman]

Summary

• Adds a toggleable Sysdig-branded color theme activated by pressing t
• Full color palette with Deep See background, Lumin green accents, and Falco Blue highlights
• Default theme output is bit-for-bit unchanged — no visual diff when theme is off
• Theme preference persists across sessions via ui-prefs.json

Details

• Two theme objects (DEFAULT_THEME, SYSDIG_THEME) with all color keys mapped
• applyTheme() swaps palette via Object.assign(C, theme) and sets per-frame background
• Conditional lineReset in render loop ensures default theme emits zero extra ANSI sequences
• Previously hardcoded model/scroll/separator colors now reference C.* theme properties
• Single-file change — no new dependencies

Test plan

• Run node index.js — confirm default theme looks identical to upstream
• Press t — confirm Sysdig theme applies (dark background, green accents, blue highlights)
• Press t again — confirm clean toggle back to default
• Restart app — confirm theme preference persists
• Resize terminal — confirm theme renders correctly at different widths

🤖 Generated with Claude Code