Initial implementation of js-post-build in rewatch #9234

Job	Run time
build-compiler (ubuntu-24.04-arm, ocaml-variants.5.3.0+options,ocaml-option-static, true, true, t...	5m 43s
build-compiler (ubuntu-24.04, ocaml-variants.5.0.0+options,ocaml-option-static, linux-x64, x86_64...	4m 54s
build-compiler (macos-15, 5.3.0, true, darwin-arm64, aarch64-apple-darwin)	8m 21s
build-compiler (windows-2025, 5.3.0, true, win32-x64, x86_64-pc-windows-gnu, .exe)	10m 48s
build-compiler (macos-15-intel, 5.3.0, true, darwin-x64, x86_64-apple-darwin)	17m 43s
build-compiler (ubuntu-24.04, ocaml-variants.5.3.0+options,ocaml-option-static, true, true, linux...	5m 7s
api-docs	1m 41s
pkg-pr-new	56s
test-integration-rewatch (macos-15)	1m 19s
test-installation-npm (ubuntu-24.04)	16s
test-installation-npm (ubuntu-24.04-arm)	19s
test-installation-pnpm (ubuntu-24.04-arm)	19s
test-installation-npm (windows-2025)	58s
test-integration-rewatch (macos-15-intel)	2m 34s
test-installation-pnpm (windows-2025)	45s
test-installation-npm (macos-15-intel)	22s
test-installation-pnpm (macos-15)	21s
test-installation-pnpm (ubuntu-24.04)	13s
test-integration-rewatch (windows-2025)	2m 56s
test-integration-rewatch (ubuntu-24.04)	1m 11s
test-installation-pnpm (macos-15-intel)	54s
test-installation-npm (macos-15)	20s
test-integration-rewatch (ubuntu-24.04-arm)	1m 10s
publish	-1s
	1h 9m 9s

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