feat: enforce canonical reconciliation handoff schema (Closes #307)

Reconciliation final reports must emit only the canonical reconciliation
handoff schema:

- Expand _RECONCILE_REQUIRED_FIELDS from 5 to the full 27-field canonical
  schema (Task through No review/merge confirmation), so incomplete
  reconciliation handoffs downgrade with per-field reasons.
- Add 'issue lock proof', 'claim/comment status', and 'workspace mutations'
  to _RECONCILE_STALE_FIELDS so stale author/reviewer fields block.
- Make the 'PR number opened' rejection conditional on a new
  session_pr_opened proof kwarg: the field is allowed only when a PR was
  actually opened in the session.
- Close the git-fetch reporting gap: a fetch observed only in the action
  log (not report text) now requires a Git ref mutations entry as well.
- Update the reconciliation handoff fixture to the canonical schema and
  add TestCanonicalReconcileSchema covering blocked, successful-close,
  and comment-only reconciliation plus missing-close-capability,
  stale-field, and conditional PR-number-opened paths.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

final_report_validator.py

@@ -101,11 +101,37 @@ _RECONCILE_STALE_FIELDS = (
     "scratch worktree used",
     "review decision",
     "merge result",
+    "issue lock proof",
+    "claim/comment status",
+    "workspace mutations",
 )
+# Issue #307: reconciliation handoffs must carry the full canonical schema.
 _RECONCILE_REQUIRED_FIELDS = (
+    "Task",
+    "Repo",
+    "Role/profile",
+    "Identity",
     "Selected PR",
-    "Eligibility class",
+    "PR live state",
+    "Candidate head SHA",
+    "Target branch",
+    "Target branch SHA",
+    "Ancestor proof",
+    "Linked issue",
     "Linked issue live status",
+    "Eligibility class",
+    "Capabilities proven",
+    "Missing capabilities",
+    "PR comments posted",
+    "Issue comments posted",
+    "PRs closed",
+    "Issues closed",
+    "Git ref mutations",
+    "Worktree mutations",
+    "MCP/Gitea mutations",
+    "External-state mutations",
+    "Read-only diagnostics",
+    "Blocker",
     "Safe next action",
     "No review/merge confirmation",
 )
@@ -346,13 +372,15 @@ def _rule_reviewer_git_fetch_readonly(
                 "classify git fetch under Git ref mutations, not read-only diagnostics",
             )
         ]
-    if not git_ref_reported and _GIT_FETCH_RE.search(text):
+    if not git_ref_reported:
+        # Issue #307: an observed git fetch (report text or action log)
+        # must be listed under Git ref mutations.
         return [
             validator_finding(
                 "reviewer.git_fetch_readonly",
                 "downgrade",
                 "Git ref mutations",
-                "git fetch mentioned without Git ref mutation classification",
+                "git fetch occurred without Git ref mutation classification",
                 "record git fetch under Git ref mutations",
             )
         ]
@@ -541,10 +569,18 @@ def _rule_reconcile_controller_handoff(report_text: str) -> list[dict[str, str]]
     return []
 
 
-def _rule_reconcile_stale_author_fields(report_text: str) -> list[dict[str, str]]:
+def _rule_reconcile_stale_author_fields(
+    report_text: str,
+    *,
+    session_pr_opened: bool = False,
+) -> list[dict[str, str]]:
     text = (report_text or "").lower()
     findings = []
     for field in _RECONCILE_STALE_FIELDS:
+        if field == "pr number opened" and session_pr_opened:
+            # Issue #307: allowed only when a PR was actually opened
+            # in this session.
+            continue
         if f"{field}:" in text:
             findings.append(
                 validator_finding(
@@ -803,6 +839,7 @@ def assess_final_report_validator(
     mutations_observed: bool = False,
     local_edits: bool = False,
     issue_filing_lock: dict | None = None,
+    session_pr_opened: bool = False,
 ) -> dict[str, Any]:
     """Validate final-report text against task-specific proof rules (#327).
 
@@ -857,6 +894,7 @@ def assess_final_report_validator(
         "action_log": action_log,
         "mutations_observed": mutations_observed,
         "local_edits": local_edits,
+        "session_pr_opened": session_pr_opened,
     }
 
     for rule in _RULES_BY_TASK.get(normalized_kind, ()):