The eight methods that derive multi-byte path edges and neighbor-confirmed edges for the mesh graph, and the NeighborEvidenceKeys tuple they return, move verbatim from app.py into modules/web_viewer/mesh_evidence.py; BotDataViewer inherits the mixin and app.py re-exports NeighborEvidenceKeys. The only textual change is an unquoted return annotation. app.py keeps timedelta and NamedTuple imported so those module attributes still resolve. The one test that froze modules.web_viewer.app.datetime to pin _compute_multibyte_evidence_edges' cutoff now freezes it where the method lives. app.py is now about 7,120 lines.
