pre-push(17.4): a file new in head is new, not comparison unknown

ChangeContext records the paths Git reports as added. An entailed,
undischarged operation in an added file, with complete head evidence and no
identical operation in any base answer, is classified new
(file_added_in_head) instead of base_incomplete; admission accepts that reason
as change evidence. Unpaired add/delete pushes and every other unknown
comparison keep their vetoes. An engine finding whose novelty is established
and whose only vetoes are capability vetoes is shown as an advisory engine
finding, not an alert. Requirement 9.4.

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01EmM1j46qgKMh3zqD1QMwEo

src/openultrasast/model/contracts.py

@@ -111,6 +111,9 @@ class ChangeContext(Contract):
     # are not encoded or decoded by this field.
     path_encoding: Literal["text", "filesystem-bytes-hex"] = "text"
     line_correspondences: tuple[LineCorrespondence, ...] = ()
+    # Paths Git reports as added (status A) in head, in this context's path encoding. A rename
+    # target is not added. Only a lexical fact: novelty still needs complete head evidence.
+    added_paths: tuple[str, ...] = ()
 
     def decode_path(self, path: str) -> str:
         """Return the filesystem spelling for matching ordinary question paths.
@@ -130,6 +133,7 @@ class ChangeContext(Contract):
                 *(s.path for s in self.spans),
                 *(p for r in self.renames for p in (r.base_path, r.head_path)),
                 *(p for m in self.line_correspondences for p in (m.base_path, m.head_path)),
+                *self.added_paths,
             ]
             for path in paths:
                 try: