Harden `Unpacker.init` re-entry cleanup to prevent buffer/context… #452

Job	Run time
Run test with Python 3.15t on ubuntu-latest	1m 14s
Run test with Python 3.11 on ubuntu-latest	28s
Run test with Python 3.14t on ubuntu-latest	1m 15s
Run test with Python 3.13 on windows-latest	1m 7s
Run test with Python 3.15 on ubuntu-latest	37s
Run test with Python 3.12 on windows-latest	1m 15s
Run test with Python 3.11 on windows-11-arm	2m 11s
Run test with Python 3.14t on windows-11-arm	3m 2s
Run test with Python 3.14 on windows-latest	1m 18s
Run test with Python 3.10 on ubuntu-latest	30s
Run test with Python 3.14 on ubuntu-latest	34s
Run test with Python 3.10 on windows-latest	1m 33s
Run test with Python 3.14t on windows-latest	2m 11s
Run test with Python 3.13 on ubuntu-latest	29s
Run test with Python 3.14 on windows-11-arm	1m 0s
Run test with Python 3.11 on macos-latest	28s
Run test with Python 3.12 on ubuntu-latest	26s
Run test with Python 3.14 on macos-latest	28s
Run test with Python 3.15t on windows-latest	2m 20s
Run test with Python 3.12 on macos-latest	23s
Run test with Python 3.15 on windows-11-arm	2m 10s
Run test with Python 3.14t on macos-latest	1m 21s
Run test with Python 3.13 on macos-latest	34s
Run test with Python 3.11 on windows-latest	1m 23s
Run test with Python 3.15t on macos-latest	1m 33s
Run test with Python 3.15t on windows-11-arm	2m 44s
Run test with Python 3.12 on windows-11-arm	1m 0s
Run test with Python 3.15 on macos-latest	1m 4s
Run test with Python 3.13 on windows-11-arm	1m 0s
Run test with Python 3.10 on macos-latest	43s
Run test with Python 3.15 on windows-latest	1m 25s
	37m 46s

Provide feedback