leasePort({closed:true}) ignored its option: it probed an ephemeral port and
closed it, so a parallel test file could bind it and answer a request the
test expected to fail (preview.test.mjs:209 saw 200 instead of 502).
leaseClosedPort holds a bound, non-listening socket in a perl child until the
test's after hook. Connects still get ECONNREFUSED, bind() from another
process gets EADDRINUSE, and the kernel's ephemeral allocation skips the port.
Lane mode keeps its band and per-port lock, and releases the socket before
the lock. leasePort now refuses a closed option, so a stale call cannot get
the unheld port again.
Unanswerable callers (webui preview, serve, service) move to leaseClosedPort(t).
Callers that listen on the port themselves (stack-release rehearse, control-board
serve, tester-cli) keep leasePort and drop the ignored option.
Candidate morgana/row244 94ab4c2fe on a36523713, manifest 6e7e3e3c (8 paths).
Webby APPROVE r1, rev 3008 (webby-0084, REVIEW-r1.md at webby/reviews
ebb3d83bf; request #1757 c30154). Gate on Sage's slot at 81e037d20
(sage-2147): the five gate-lane files whole 51/0, test-task.sh 91/0,
test-release.sh 14/0, mutants M-G, M-L, M-A, M-T and M-F killed.
94ab4c2fe adds only BUILD.md results. Webby's drift check: a36523713..d37210288
changes none of the 8 paths and no path either suite reads; merge-tree clean.
Rulings A and C (sage-1914, sage-2061). The dropped real-model coverage goes
to DEFERRED in the follow-up doc commit.