Remove shared-module mocks for input reads, heap statistics, and tarball streaming. Exercise actual file changes and real V8 heap admission in fresh CLI processes; keep only selected-descriptor syscall fault injection for the pathless EIO case.
Reproduced the four hosted source failures with a preloaded module graph and found the same flaw in the adjacent tarball test. The preloaded control now passes 17 cases; 32 focused tests, all 1,739 service tests (2 skips), and check:ci pass. Snapshot, cleanup, identity, and error projection coverage is retained.
