Bump to TypeScript 5.6 /w strictPropertyInit #1539

Job	Run time
pylint (macos)	11s
lint (npm run lint:eslint, macos)	1m 43s
pylint (ubuntu)	20s
lint (npm run lint:eslint, ubuntu)	1m 37s
todo-check	4s
pylint (windows)	50s
lint (npm run lint:eslint, windows)	3m 34s
lint (npm run lint:yaml, macos)	56s
validate-collection-files (macos)	13s
lint (npm run lint:yaml, ubuntu)	51s
lint (npm run lint:yaml, windows)	4m 1s
lint (npm run lint:md, macos)	1m 0s
validate-collection-files (ubuntu)	21s
lint (npm run lint:md, ubuntu)	55s
lint (npm run lint:md, windows)	2m 44s
validate-collection-files (windows)	58s
lint (npm run lint:md:consistency, macos)	58s
lint (npm run lint:md:consistency, ubuntu)	49s
lint (npm run lint:md:consistency, windows)	3m 48s
lint (npm run lint:md:relative-urls, macos)	1m 22s
lint (npm run lint:md:relative-urls, ubuntu)	1m 11s
lint (npm run lint:md:relative-urls, windows)	5m 18s
lint (npm run lint:md:external-urls, macos)	2m 14s
lint (npm run lint:md:external-urls, ubuntu)	2m 54s
lint (npm run lint:md:external-urls, windows)	6m 8s
	45m 0s

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