Bump to TypeScript 5.6 /w strictPropertyInit #1540

Job	Run time
lint (npm run lint:eslint, macos)	1m 28s
pylint (macos)	14s
lint (npm run lint:eslint, ubuntu)	1m 43s
pylint (ubuntu)	24s
validate-collection-files (macos)	14s
pylint (windows)	53s
todo-check	2s
lint (npm run lint:eslint, windows)	4m 9s
validate-collection-files (ubuntu)	22s
lint (npm run lint:yaml, macos)	54s
validate-collection-files (windows)	1m 3s
lint (npm run lint:yaml, ubuntu)	56s
lint (npm run lint:yaml, windows)	4m 24s
lint (npm run lint:md, macos)	1m 15s
lint (npm run lint:md, ubuntu)	50s
lint (npm run lint:md, windows)	6m 5s
lint (npm run lint:md:consistency, macos)	56s
lint (npm run lint:md:consistency, ubuntu)	49s
lint (npm run lint:md:consistency, windows)	4m 3s
lint (npm run lint:md:relative-urls, macos)	57s
lint (npm run lint:md:relative-urls, ubuntu)	49s
lint (npm run lint:md:relative-urls, windows)	5m 59s
lint (npm run lint:md:external-urls, macos)	2m 13s
lint (npm run lint:md:external-urls, ubuntu)	2m 21s
lint (npm run lint:md:external-urls, windows)	5m 45s
	48m 48s

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