Same contract as issue-comment (PR #1462): -b/--body canonical comment
flag with -c/--comment alias; usage errors stderr + exit 2 (unknown
option, missing -i, value-less flags); provider failures normalized to
exit 1 on the GitHub path (gh's own usage errors exit 2 and would
collide with the reserved status).
New suite test-issue-close-usage-contract.sh, enrolled in
framework-shell CI (enumeration guard OK, population 74). Probe
assertions split: parser arms must contact zero providers; sandbox arms
may issue detection reads only (tea login list), never gh/curl.
Existing fail-closed suite still green. Mirrored to the brain tree.
marcie
7a38eed18a