fix(slab): O(1) aligned-page cross-thread frees + retire-on-live-count (closes #852) #518

Job	Run time
security / security-static	31s
security / codeql-gate	35m 37s
lint / lint	3m 8s
security / license-gate	2m 45s
test / setup-matrix	2s
test / test-windows-guards	7m 39s
test / test-windows (windows-latest, CLANG64, x86_64)	34m 9s
test / test-unix (macos-15-intel, cc, c++)	17m 46s
test / test-unix (ubuntu-24.04-arm, gcc, g++)	1h 12m 11s
test / test-unix (macos-14, cc, c++)	16m 6s
test / test-unix (ubuntu-latest, gcc, g++, true)	12m 51s
ci-ok	4s
security / codeql-gate	35m 37s
security / license-gate	2m 45s
test / test-unix (ubuntu-latest, gcc, g++, true)	12m 54s
test / test-windows (windows-latest, CLANG64, x86_64)	34m 9s
test / setup-matrix	2s
test / test-windows-guards	7m 39s
test / test-unix (macos-14, cc, c++)	16m 6s
test / test-unix (ubuntu-24.04-arm, gcc, g++)	1h 12m 11s
test / test-unix (macos-15-intel, cc, c++)	17m 46s
security / security-static	31s
lint / lint	3m 8s
ci-ok	3s
	6h 45m 40s

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