Import Iterable in build.py, the annotations already use it

build.py annotates chunks and ast_sources with Iterable but never imports it, so
ruff reports four F821 on v8 and typing.get_type_hints() raises on
_tier_replacement_sources, merge_raw_extraction and build_merge. Nothing breaks at
import because `from __future__ import annotations` keeps the hints as strings.

The added test walks build.py's own functions rather than the package: nx under
if TYPE_CHECKING in cross_repo_calls.py, cross_repo_types.py and prs.py is
unresolvable on purpose, while build.py imports every annotated name at module scope.

(cherry picked from commit c315a15c24)

graphify/build.py

@@ -27,6 +27,7 @@ import os
 import re
 import sys
 import unicodedata
+from collections.abc import Iterable
 from pathlib import Path
 import networkx as nx
 from .ids import make_id, normalize_id as _normalize_id

tests/test_build.py

@@ -1983,3 +1983,21 @@ def test_build_merge_explicit_ast_sources_argument(tmp_path):
 
     G1 = build_merge([sln_chunk], graph_path, dedup=False, root=root, ast_sources=["A.sln"])
     assert "nuget_pkg" in G1, "ast_sources explicit arg must protect undispatched A.csproj"
+
+
+def test_build_annotations_all_resolve():
+    # build.py imports every annotated name at module scope -- no TYPE_CHECKING-only
+    # names -- so an unresolvable hint here means a missing import, not a lazy one.
+    import inspect
+    import typing
+
+    from graphify import build as build_module
+
+    unresolvable = []
+    for name, obj in vars(build_module).items():
+        if inspect.isfunction(obj) and obj.__module__ == build_module.__name__:
+            try:
+                typing.get_type_hints(obj)
+            except NameError as exc:
+                unresolvable.append(f"{name}: {exc}")
+    assert not unresolvable, "\n".join(unresolvable)