Identify and implement top 5 code reduction

Identify top 5 opportunities to massively reduce the amount of code (lines of code) in any part of the repo: - Similar functionality that can be unified and reused - Code that has been valuable but no more - A front end component or a group of them duplicate another component/page functionality. Use the most modern and nice looking - etc. Now implement them :)

Five folds landed (net −85 lines, 23 files): api test HTTP doubles onto tests/http_fakes (ChunkStream/chunked, mock_transport(attr=), network_shaped, route_client, memory_bucket); web applyPendingDispatch; jaahd commands.refused_reply. Quick gate, 1271+434 api, 663 web, 277 jaahd tests green; both blind lanes pass. PR #7941 queued to the merge lane. Assumed "massive" admits what eleven prior passes left: recon found no dead file or clone. No UI surface affected. Memory: used mem-25288, mem-36366; proposed none.