Preserve \src attributes through classic abc pass #14

Job	Run time
pre_job	4s
pre_docs_job	6s
Reusable build (macos-latest)	17m 53s
Reusable build (ubuntu-latest)	18m 9s
Try build docs	0s
Run docs tests (ubuntu-latest)	36s
Run test_cell (ubuntu-latest)	1m 28s
Run tests (ubuntu-latest)	10m 9s
Run tests (macos-latest)	15m 5s
	1h 3m 30s

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