Move the single-implementer dispatch mechanism from csharp_dispatch.py
into interface_dispatch.py with the file-suffix gate as a keyword
parameter. csharp_dispatch.py keeps its public names
(resolve_csharp_interface_dispatch, _method_label, DISPATCH_RELATION)
and becomes the `.cs` gate over the core. No behaviour change: the 15
C# dispatch tests pass untouched, and the extractor registration is
not modified.
Swift protocols have the same shape (#3673 resolves a call through an
injected protocol to the requirement, and the conformer's method sits
unreachable from it). With the core shared, that language can add a
gate instead of a second copy of the algorithm.
AI disclosure: Claude Code assisted with this change.
(cherry picked from commit 6aade32806)
GAURAV singh
0bd22d4bee