Migrate entire experts to base16 palette

The experts command (plain output + interactive TUI) was missed by the base16 migration and still carried its own Tailwind-400 hex colors (#fb923c, #22d3ee, #818cf8) and extended 256-color codes (245, 241), so it ignored the user's terminal theme.

Route every experts style through cmd/entire/cli/palette:

• orange accent (title/agent/bullet/selected/section) -> palette.Accent (magenta)
• cyan (label/file) -> palette.Info
• indigo (facet) -> palette.Blue
• grays 8/241/245 -> palette.Muted, with Faint(true) for the dimmest help tier

Update the self-contained TestRenderExpertsWithStylesUsesEntirePalette fixture to the palette constants so the assertion matches the migration.