Update hyparquet to 1.28.1 and @types/node to 26.2.0. Hold typescript at
6.0.3: version 7 fails the build with two type errors in the sinks driver.

Fix two tests that only passed on a Linux host or on Node 24 and below:
the usage-policy fold test counted every event when it meant the fold
events alone, so the live darwin case probe's case_probe_skipped tripped
it; the blob-store ifNoneMatch test discarded a getObject body and leaked
its FileHandle, which Node 26 now treats as an error.