fix(csv): purchase IDs say 80pct on --input-csv runs that buy 100% #2248

Problem

effectiveSizingPct (cmd/main.go:289) feeds the purchase-ID labels (cmd/multi_service_helpers.go:289 and :301). On an --input-csv run without --coverage, the run buys 100% of the CSV counts, but the purchase IDs are labelled 80pct. So the label disagrees with what was bought.

Found during the independent review of #2247. That PR doesn't cause this; it fixes the explicit --coverage 80 case, and the label mismatch was already there.

Expected

The sizing label reflects the coverage actually applied: 100pct, or no coverage label, on a CSV run without the flag. Ideally it comes from the same function as the sizing (determineCSVCoverage), so the two cannot drift.

Check first

Do any consumers parse or compare these purchase IDs (idempotency, dedupe, audit)? If so, changing the label for new runs must not break matching against older IDs.