Fix slotted reference cycles on 3.14 (#1446) #1622

Job	Run time
Check types using pyright	15s
Build & verify package	23s
Verify dev env	12s
Run doctests & render changelog	17s
Tests & Mypy on 3.10	1m 10s
Tests on pypy-3.10	21s
Tests & Mypy on 3.11	1m 4s
Tests & Mypy on 3.13	1m 3s
Tests & Mypy on 3.14	2m 6s
Tests & Mypy on 3.9	27s
Tests & Mypy on 3.12	1m 2s
Combine & check coverage	9s
required-checks-pass	4s
	8m 33s

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