feat(ttp): E.3.8 R0041-R0048 email cohort

8 YAMLs for the email cohort per Appendix B: open-relay abuse,
mass phishing, phishing-kit X-Mailer signatures, IDN/punycode
URLs, sender masquerade, malicious attachment, BEC, encoded
payload in body. EmailLifter (E.3.12) consumes by rule_id.

test_email_rules.py: YAML-present + inert-in-v0 + xfail(strict)
precision case gated on E.3.12.

tests/ttp/rule_precision/test_email_rules.py

@@ -0,0 +1,54 @@
+"""R0041-R0048 — email cohort.
+
+EmailLifter (E.3.12) consumes these by rule_id. The v0
+:class:`RuleEngine` cannot parse SMTP envelopes, walk attachment
+trees, or compose header / body / attachment signals — so these
+rules are inert under the regex matcher.
+
+Asserts each YAML compiles, none fire from the v0 engine, and a
+strict-xfail precision case that flips green when E.3.12 lands.
+"""
+from __future__ import annotations
+
+from collections.abc import Callable
+from pathlib import Path
+
+import pytest
+
+from decnet.ttp.impl.rule_engine import RuleEngine
+from decnet.ttp.store.base import RuleState
+from decnet.ttp.store.impl.filesystem import _parse_and_compile
+from tests.ttp.rule_precision.conftest import CorpusRow, make_event
+
+CohortLoader = Callable[[str], list[CorpusRow]]
+
+_RULE_IDS = [f"R{n:04d}" for n in range(41, 49)]
+
+
+@pytest.mark.parametrize("rule_id", _RULE_IDS)
+def test_rule_yaml_present(rule_id: str) -> None:
+    path = Path("rules/ttp") / f"{rule_id}.yaml"
+    assert path.exists(), f"missing YAML: {path}"
+    compiled = _parse_and_compile(path, RuleState())
+    assert compiled.rule_id == rule_id
+
+
+@pytest.mark.parametrize("rule_id", _RULE_IDS)
+async def test_lifter_bound_inert_in_v0(
+    rule_id: str,
+    precision_engine: RuleEngine,
+    corpus_loader: CohortLoader,
+) -> None:
+    fired: set[str] = set()
+    for row in corpus_loader("email"):
+        tags = await precision_engine.evaluate(make_event(row))
+        fired.update(tag.rule_id for tag in tags)
+    assert rule_id not in fired, (
+        f"{rule_id} is lifter-bound but fired from the regex engine"
+    )
+
+
+@pytest.mark.parametrize("rule_id", _RULE_IDS)
+@pytest.mark.xfail(strict=True, reason="impl phase E.3.12 (EmailLifter)")
+def test_email_rule_precision(rule_id: str) -> None:
+    pytest.fail(f"{rule_id}: EmailLifter not yet shipped (E.3.12)")