test(scripts): stop fake go stub looping forever

[wstein]

The fake go stubs in scripts/install_test.go ended in a shift loop that never terminates for any call without -o (99% CPU, orphaned when the test ended: two such processes ran for 18 h). Both stubs now exit 2 when no -o is found; make runs in its own process group with a 3-minute deadline and a group kill on cancel and in cleanup; a regression test fails on the old stub.

Opus review: CLEAR at 3653290. The reviewer reproduced the orphan (old stub behind a Makefile calling go env GOFLAGS, make killed with -9: child survived with ppid 1), verified process-group handling on macOS (hang in a shell function, in a recipe, and a failing test: all killed, nothing left), caught the old-stub mutation, scanned 43 test files with shell stubs and found no other unbounded loop. Lows noted on #399: go test -timeout shorter than 3 min skips cleanups; the second stub copy has no direct guard; one barrier loop in board_snapshot_test.go is unbounded only if the test panics.

Refs: #399

🤖 Generated with Claude Code

[wstein]

Opus review CLEAR at 3653290: orphan reproduced (old stub behind a Makefile calling go env GOFLAGS, make killed with -9, child survived with ppid 1), process-group kill verified on macOS for a hang in a shell function, in a recipe and for a failing test, regression test fails on the old stub, 43 test files with shell stubs scanned with no other unbounded loop, go test ./... and make check-ci exit 0. Lows (go test -timeout shorter than 3 min, second stub copy unguarded, one barrier loop in board_snapshot_test.go) go to #399.

Co-Authored-By: Claude Sonnet 5.5 [email protected]