Catalog: the sender keep-out, the event stream and the page's call leave

Three catalog tests leave for the host proofs that carry them; the
catalog goes from 91 to 88. Each proof passed; none skipped.

- exthost.sender-keep-out, for forgeext's run_test.py (ebdbf59): a
  package granted sender.keep_out posts /v0/sender {"out": true}, the
  stand-in takes it only with the host's token, and the claim is kept
  fresh beside the holds, raised in the host's words, until the package
  is disabled. The machine's side is forgectrl's senderout_test.
  suite/extsender.py held only it: the module and its import go.
- exthost.events, for forgeext's run_test.py (ebdbf59) and forgectrl's
  host_lan.sh (b272b3a): the host holds one stream while a package wants
  events and lets it go when none does, a poll at the head comes back
  empty at its one-second deadline, a waiting poll is answered 0.10 s
  after an event; and the host's slot is a loopback peer's alone, the
  same header from a LAN address leaving the host's stream open.
  forgeext's evfeed_test and forgectrl's events_test hold the two
  daemons' own sides. Its section header, the operator's door, held
  only it, and EVENTS_MAX_STREAMS, EVENTS_HOST_HEADER and _stream, which
  only it read, go with it.
- exthost.page-call, for forgeext's sdk_test.py (ebdbf59): disabled, the
  page package's socket name is gone and its call is refused in the
  host's words; enabled, the same call answers 200. sdk_test.py already
  held the calls, their form and refusals, and the frozen service;
  forgectrl's extpkg_test holds the relay. suite/extcall.py held only
  it: the module and its import go.

The coverage lint then named forgectrl src/senderout.c and
src/senderout.h, and nothing else; one HOST_TESTED row takes them, to
forgectrl:tests/senderout_test.c on forgectrl:.github/workflows/build.yml,
which the pin c274f19 runs. grblhal-glowforge's src/serial.* stays
covered by a catalog test and gets no row; holdkeep, evfeed, call and
sandbox stay under exthost.service's forgeext/**, and forgectrl's
src/events.* under forgectrl.lease.

test_setup_suite.py (31) and test_manifest.py (34) pass. The coverage
lint on the tree manifest finds no uncovered path and no host-tested row
problem across the 88 tests; its one finding is setup.check-lens's
empty src/lensfind.* entry. pyflakes reports nothing on exthost.py or
manifest.py. The full forgetest suite was not run.

Fingerprints: exthost.py's shared text moves, so 9 tests move: the 7
left in exthost.py, and exthost.catalog and exthost.wizard in the
modules that read it. The pending pin bump from c274f19 already owes 8
of them; exthost.platform is the one it adds, as before. releases/ and
TEST-AUDIT.md are unchanged.

forgetest/forgetest/manifest.py

@@ -140,6 +140,10 @@ HOST_TESTED = [
     # The setup record as a printable page: no script, the sheet id, a
     # heading for each completed step, everything escaped.
     ("forgectrl", "src/recordhtml.*", "forgectrl:tests/recordhtml_test.c", "forgectrl:.github/workflows/build.yml"),
+    # An extension package's claim on the Grbl sender as the machine keeps
+    # it: the claim and its refusals, its end by the package, the operator
+    # or a stale keeper (forgeext's run_test proves the writer's side).
+    ("forgectrl", "src/senderout.*", "forgectrl:tests/senderout_test.c", "forgectrl:.github/workflows/build.yml"),
 ]
 
 # This repository's root, when the package runs from a checkout of it; a