feat: require live PR head re-pin before conflict-fix classification (Closes #522)

Treat inventory mergeable/head as advisory. Add classification helper and
MCP tool so author sessions re-pin the live PR head before creating a
conflict-fix worktree, skip stale inventory false-negatives, and prove
classification in final reports.

gitea_mcp_server.py

@@ -827,6 +827,7 @@ import reconciliation_workflow  # noqa: E402
 import audit_reconciliation_mode  # noqa: E402
 import review_merge_state_machine  # noqa: E402
 import pr_work_lease  # noqa: E402
+import conflict_fix_classification  # noqa: E402
 import native_mcp_preference  # noqa: E402
 import worktree_cleanup_audit  # noqa: E402
 
@@ -8209,6 +8210,40 @@ def gitea_acquire_conflict_fix_lease(
     }
 
 
+@mcp.tool()
+def gitea_assess_conflict_fix_classification(
+    pr_number: int,
+    inventory_head_sha: str | None = None,
+    inventory_mergeable: bool | None = None,
+    live_head_sha: str | None = None,
+    live_mergeable: bool | None = None,
+) -> dict:
+    """Read-only: classify conflict-fix need from live PR state (#522).
+
+    Open PR inventory can be stale. Callers must pass a live re-fetched PR head
+    and mergeability value before creating a conflict-fix worktree.
+    """
+    read_block = _profile_operation_gate("gitea.read")
+    if read_block:
+        return {
+            "success": False,
+            "performed": False,
+            "reasons": read_block,
+            "permission_report": _permission_block_report("gitea.read"),
+        }
+
+    result = conflict_fix_classification.assess_conflict_fix_classification(
+        pr_number=pr_number,
+        inventory_head_sha=inventory_head_sha,
+        inventory_mergeable=inventory_mergeable,
+        live_head_sha=live_head_sha,
+        live_mergeable=live_mergeable,
+    )
+    result["success"] = True
+    result["performed"] = False
+    return result
+
+
 @mcp.tool()
 def gitea_assess_conflict_fix_push(
     pr_number: int,