Identify and implement top five 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 :)

Identified the five largest code-reduction levers (Windows nodes 15.6k, macOS nodes 6.8k, legacy terminal runtime, ~880-line fleet-migration bridges, ~2.3k dev tooling in the API image); each needs a product or fleet decision. Whole-repo census found no mechanical duplication or dead code left (earlier sweeps shipped it), so no PR. Report uploaded. No UI surface affected. Memory: used mem-32217, mem-32705, mem-30919, mem-31292, mem-32347, mem-31300, mem-27843; proposed 1 qa.