### S1.3.1 — Benchmark foundation
- [x] Add Criterion as a development dependency
- [x] Add a dedicated `scan` benchmark target
- [x] Measure 1 KiB, 64 KiB, and 1 MiB inputs
- [x] Measure 4, 64, and 512-rule sets
- [x] Measure zero, sparse, and dense findings
- [x] Measure literal, prefix, suffix, regex, and mixed workloads
- [ ] Record the first serial baseline
- [ ] Document benchmark environment and commands
- [ ] Define a performance-regression policy before optimization work