Sub-step preceding the rule-pack commits per TTP_TAGGING.md:2967.
Adds the per-rule precision suite scaffolding under
tests/ttp/rule_precision/:
- conftest.py: precision_engine fixture (RuleEngine populated from
./rules/ttp/), corpus_loader (real → seed → empty fallback),
precision_for() helper for TP/FP accounting.
- _build_corpus.py: extractor for a real prod corpus pull. Mandatory
--exclude-ip / DECNET_TTP_CORPUS_EXCLUDE_IPS — operator IPs never
end up in the committed exclusion list. Pulls both 'command' and
'unknown_command' event types.
- corpus/seed_*.jsonl: synthetic seed rows for each cohort so the
harness exercises in clean checkouts.
- corpus/*.jsonl (operator-built) is gitignored.
- test_corpus_loads.py: sentinel that every seed file parses.
