Fix rewatch panic on duplicate module name #9079

Job	Run time
build-compiler (windows-2025, 5.3.0, true, win32-x64, x86_64-pc-windows-gnu, .exe)	10m 50s
build-compiler (macos-15-intel, 5.3.0, true, darwin-x64, x86_64-apple-darwin)	10m 51s
build-compiler (ubuntu-24.04, ocaml-variants.5.3.0+options,ocaml-option-static, true, true, linux...	5m 9s
build-compiler (ubuntu-24.04, ocaml-variants.5.0.0+options,ocaml-option-static, linux-x64, x86_64...	4m 59s
build-compiler (ubuntu-24.04-arm, ocaml-variants.5.3.0+options,ocaml-option-static, true, true, t...	5m 43s
build-compiler (macos-15, 5.3.0, true, darwin-arm64, aarch64-apple-darwin)	6m 13s
pkg-pr-new	54s
api-docs	1m 28s
test-installation-pnpm (windows-2025)	33s
test-installation-pnpm (macos-15)	16s
test-installation-pnpm (ubuntu-24.04)	16s
test-installation-pnpm (macos-15-intel)	35s
test-installation-pnpm (ubuntu-24.04-arm)	17s
test-integration-rewatch (ubuntu-24.04)	1m 20s
test-installation-npm (ubuntu-24.04)	13s
test-installation-npm (macos-15)	18s
test-integration-rewatch (macos-15-intel)	3m 2s
test-installation-npm (macos-15-intel)	25s
test-integration-rewatch (windows-2025)	3m 2s
test-integration-rewatch (ubuntu-24.04-arm)	1m 7s
test-installation-npm (ubuntu-24.04-arm)	16s
test-installation-npm (windows-2025)	47s
test-integration-rewatch (macos-15)	1m 27s
publish	0s
	1h 0m 1s

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