Change format from verbose emoji-based message to cleaner status line:
Before: ✨🥒 Context thinned at 70%: 7 tool results, ~33839 chars saved ✨
After: g3: thinning context ... 70% -> 40% ... [done]
The new format shows before/after percentages and uses bold green for
'g3:' and '[done]' to match other status messages.
Also removes unused emoji() and label() methods from ThinScope.