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ci + release: gate main on all five suites; one version, tag and draft release per bump; npm on publish #27

Job	Run time
repo invariants	10s
build & typecheck	42s
what changed	6s
engine (python)	5m 20s
engine (javascript)	35s
engine (csharp)	34s
engine (java)	36s
engine (typescript)	35s
engines build on every platform	0s
CI	3s
	8m 41s