test(inventory): exclude build outputs from the repo-write inventory

The sandbox marker refusal matrix takes a before/after repository inventory for
each of nine cases. target and dist were walked, so on a working clone the walk
covered ~44k entries, core/target alone contributing ~23k files at ~7 GB, and
eighteen full walks pushed the test past pytest 15s timeout. A clean checkout of
the same commit walks ~73 MB and the same test passes in 1.75s, so the verdict
depended on how much the clone had been built in rather than on the product.

target and dist are build outputs, not repository source, and cargo and uv
rewrite them constantly. That is the same category as the .venv and cache
entries already in this set, whose name says runtime dir names.

The exclusion cannot blind the check: tests/test_repo_inventory.py parametrizes
its visibility cases over this set, so both new names automatically gain the
proofs that a regular file, symlink, or fifo with that basename stays
inventoried and that a symlink by that name is not followed, alongside the
existing proof that ordinary writes are reported. 99 inventory tests pass.