perf: eliminate dead code from minified skill scripts

After `drop_console: true` removes console.* calls, Terser left behind
constants that were only used for console output (e.g. the RATING object
with emoji icons/colors like { good: { icon: "🟢", color: "#0CCE6A" }, ... }).

This happened because Terser's single-pass compression couldn't determine
that destructured values from those constants were unused after console
removal.

Fix: add two Terser compress options:
- `pure_getters: true` — tells Terser that property accesses (obj.prop,
  obj[key]) have no side effects, so unused destructured results can be
  safely dropped
- `passes: 2` — runs a second compression pass to eliminate secondary dead
  code (unused variables whose only consumers were already removed in the
  first pass)

Result: emoji/color constants and their associated destructuring assignments
are fully eliminated from the generated skill scripts, reducing token
footprint further.

Author: nucliweb