fix(pr-review): reject a verdict that contradicts the review's findings

post_pr_review (inbound external/fork PR review) derived both the recorded
notes_structured.pr_review.verdict AND the posted GitHub review event solely
from its `event` argument, which defaults to REQUEST_CHANGES — and, unlike the
in-path gate's pr_fail, it never required any findings. A reviewer that
concluded 'approve' in the summary but left event at the default filed (and
posted to the contributor's PR) a blocking 'changes requested' with nothing
cited, contradicting the approving summary the CEO saw on the PR Reviewer Notes
card.

Enforce a verdict<->findings invariant before any record or GitHub post:
- REQUEST_CHANGES must cite >=1 finding (almost always a forgotten
  event='APPROVE'), mirroring pr_fail's 'at least one issue' rule;
- APPROVE may not carry a blocker/major finding.
The check is the pure policy fn pr_review_conflict() wired through the new
choreographer _verdict_consistency_gate, rejected with a clear remediate hint.
Steer the agent at the source too: the flow MCP tool + request schema now spell
out the invariant and to pass event='APPROVE' explicitly for a clean PR.

tests/unit/foundation/policy/content/test_pr_review_conflict.py

@@ -0,0 +1,67 @@
+"""The PR-review verdict<->findings invariant.
+
+A reviewer's recorded verdict and the GitHub review event both derive from the
+``event`` argument, so they must agree with the findings the reviewer cites.
+``pr_review_conflict`` is the pure predicate the gateway enforces before any
+review is recorded or posted — so an approving review can never be filed (or
+posted to a contributor's PR) as a blocking "changes requested", and an
+approval can never sail over a blocker.
+"""
+
+from __future__ import annotations
+
+from roboco.foundation.policy.content import pr_review_conflict
+
+_BLOCKER = {"file": "a.py", "severity": "blocker", "expected": "x", "actual": "y"}
+_MAJOR = {"file": "a.py", "severity": "major", "expected": "x", "actual": "y"}
+_MINOR = {"file": "a.py", "severity": "minor", "expected": "x", "actual": "y"}
+_NIT = {"file": "a.py", "severity": "nit", "expected": "x", "actual": "y"}
+
+
+def test_request_changes_with_no_findings_conflicts() -> None:
+    # The reported bug: REQUEST_CHANGES (the default) with zero findings — a
+    # blocking verdict with nothing cited, contradicting an approving summary.
+    conflict = pr_review_conflict("REQUEST_CHANGES", [])
+    assert conflict is not None
+    message, remediate = conflict
+    assert "finding" in message.lower()
+    assert "APPROVE" in remediate
+
+
+def test_request_changes_with_a_finding_is_ok() -> None:
+    assert pr_review_conflict("REQUEST_CHANGES", [_MINOR]) is None
+
+
+def test_approve_over_a_blocker_conflicts() -> None:
+    conflict = pr_review_conflict("APPROVE", [_BLOCKER])
+    assert conflict is not None
+    message, _ = conflict
+    assert "approve" in message.lower()
+
+
+def test_approve_over_a_major_conflicts() -> None:
+    assert pr_review_conflict("APPROVE", [_MAJOR]) is not None
+
+
+def test_approve_with_only_nits_is_ok() -> None:
+    assert pr_review_conflict("APPROVE", [_NIT, _MINOR]) is None
+
+
+def test_approve_with_no_findings_is_ok() -> None:
+    assert pr_review_conflict("APPROVE", []) is None
+
+
+def test_comment_is_never_in_conflict() -> None:
+    # A neutral COMMENT carries no verdict, so it is never a contradiction.
+    assert pr_review_conflict("COMMENT", []) is None
+    assert pr_review_conflict("COMMENT", [_BLOCKER]) is None
+
+
+def test_findings_none_is_treated_as_empty() -> None:
+    assert pr_review_conflict("REQUEST_CHANGES", None) is not None
+    assert pr_review_conflict("APPROVE", None) is None
+
+
+def test_severity_match_is_case_insensitive() -> None:
+    upper = {"file": "a.py", "severity": "BLOCKER", "expected": "x", "actual": "y"}
+    assert pr_review_conflict("APPROVE", [upper]) is not None