golden-capture-provenance accept() left a ~20 MB baselines sandbox in
TMPDIR on every call (433 copies, 8.5 GB, ENOSPC in the shared sandbox).
It now reads what it needs and removes the sandbox in finally; fixtures
are removed via t.after. Same fix for the three other leaking sites
(bundle-assets hp-tree-, docs-accept hp-identical-, rebase-generated
hp-runner- outside finally).
test/temp-dir-hygiene.test.mjs parses test/**/*.mjs with the TypeScript
AST: every mkdtemp/mkdtempSync must be bound to a name removed by
rm*/rmSync in a finally block or an after/afterEach/t.after hook of the
same function, or returned by a named helper whose every call site does
so; exception `// tmp-ok: <reason>`. Two mutants witness the lint.
Issue: #646
User-Visible: no
