fix: --fail-on-waste 0 no longer fails clean repos

[wellparth]

Summary

Fixes #19. wastePct (0) >= 0 is always true, so --fail-on-waste 0 could never pass — a clean repo (0% waste) exited 1, breaking CI that wires a 0% gate.

Fix

In src/cli.js, the fail check now also requires actual waste:

if (o.failOnWaste != null && scan.totals.wastePct >= o.failOnWaste && scan.totals.wastePct > 0) return 1;

• --fail-on-waste 0 on a clean repo → exit 0 (waste is 0, nothing to fail on)
• --fail-on-waste 0 on a repo with any waste → still exit 1
• All non-zero thresholds keep their existing >= semantics (verified: fixture at exactly 100% waste still fails --fail-on-waste 100)

Tests

Added three CLI tests (TDD — failing before the fix):

1. clean repo + --fail-on-waste 0 exits 0
2. dirty repo + --fail-on-waste 0 still exits 1
3. threshold boundary: 100% waste fails at threshold 100, 1% threshold catches waste, clean repo passes 50% threshold

Housekeeping

• Version bumped 0.1.4 → 0.1.5, CHANGELOG entry added (per CONTRIBUTING.md)

Verification

npm test → 14/14 passing.