CLI integration tests spawned the real fabro binary while letting the
parent process's env pass through. The pr_view "no credentials" snapshot
failed in CI because the Nightly workflow's minted GITHUB_TOKEN was
inherited by the child and turned the expected "credentials required"
error into a real GitHub API call (404 / 401). On developer laptops the
same leak occurs whenever gh auth login is active.
Introduce apply_test_isolation(cmd, home) in fabro-test: env_clear() +
re-populate PATH, HOME, NO_COLOR, and the FABRO_* test overrides. Route
TestContext::command(), the internal server bootstrap, and the four
ad-hoc spawners in tests/it/cmd/{attach,render_graph,runner,server_start}
through the same helper so the isolation is systemic instead of
per-callsite. Tests that deliberately need a credential (OPENAI_API_KEY,
GITHUB_APP_PRIVATE_KEY, etc.) continue to set it explicitly on the
returned Command; those survive the clear.
Add a regression test that sets sentinel GITHUB_TOKEN and
ANTHROPIC_API_KEY in the parent, spawns /usr/bin/env through the helper,
and asserts the child sees neither credential while still seeing PATH
and the harness's FABRO_NO_UPGRADE_CHECK override.
Verified: the full workspace (4022 tests) passes with GITHUB_TOKEN and
ANTHROPIC_API_KEY set in the parent, which previously broke the
pr_view_reads_pull_request_from_store_without_pull_request_json
snapshot. cargo fmt and nightly clippy are clean.
Keep the render-graph CLI integration test explicitly documented for
synchronous stdio subprocess usage, and make the garbage-stdout server
test drain stdin before returning invalid output so the Linux test path
stays deterministic.
Run Graphviz through an internal fabro subprocess so renderer failures no
longer share process fate with the server. Keep expected DOT parse failures
on the 400 path via an explicit stdout protocol, and treat child crashes or
protocol violations as 500s.
