- issue-list + milestone-create: usage() default exit 2, value guards,
missing-title via usage_error.
- lane-brief: getopts replaced with a while/case parser carrying R2
long-flag aliases (--repo --milestone --label/--labels --login
--limit) beside the short forms; login-resolution failure reclassified
from exit 2 to exit 1 (credential class, not an invocation defect).
- Three suites enrolled (population 88); lane-brief pr-linkage suite
still ALL PASS; green in both trees; mirrored to the brain tree.
With this, every agent-facing wrapper in tools/git carries the R1/R4
usage-error contract (22/22 non-guard wrappers; guards keep their own
contracts).