DedupHITLToolCallsMiddleware is only wired by the main_agent stack, but
its module also exports dedup-key resolvers consumed by the shared MCP
tool layer. Splitting keeps the resolvers (dedup_key_full_args,
wrap_dedup_key_by_arg_name, DedupResolver) in shared and moves the
middleware class verbatim into main_agent/middleware/dedup_hitl.py
(merged with its builder), eliminating the shared->main_agent dependency
that a flat move would create. No behavior change.
fbd5ccc35a