Let the page run a campaign's remaining tests as a queue

A campaign is mostly waiting for the next Start. The page now offers two
queues, and each takes every test of its kinds the campaign does not
already count as satisfied: Unattended for the auto tests, which need
nobody in the room, and Operator and live for the ones that need somebody
at the machine, since they prompt and they fire the laser. The buttons
say how many they would run and ask before starting; the live queue names
the tests that fire and takes the acknowledgment once, for all of them.

A queue runs one test at a time through the runner's single slot, in
prerequisite order. Registration order otherwise, so a run reads down the
page, but a prerequisite inside the queue always goes first. It stops on
the first result that is not a PASS: a FAIL closes the campaign, and
carrying on would only open a second one behind the operator's back. A
test the runner refuses to start is skipped with the reason on the page
and the rest carry on, which is what happens to an auto test waiting on an
operator one: run the attended queue, then the unattended one again.

The queue lives in the runner, not in the tab, so reloading the page or
closing it leaves the run alone. While one is up it holds the machine
between its tests as well as during them, so a single Start and the bench
tools are refused rather than cutting in. Stop the queue cancels what is
still waiting and lets the run in progress finish; Abort ends that one
too, and lands as the non-PASS that stops the queue. Every run a queue
starts records which one put it there.

Also moves the /state ETag test to the end of its class. It invalidates,
timestamps are whole seconds, and a PASS stamped in the same second as an
invalidate is deliberately not inheritable, so on a fast run it decided
the inheritance an earlier test was checking.

forgetest is a dev-only component and can never appear in a coverage map,
so this has no acceptance catalog consequence.

forgetest/forgetest/catalog.py

@@ -120,6 +120,35 @@ def get(id, registry=None):
     return (registry if registry is not None else REGISTRY).get(id)
 
 
+def order_by_requires(tests, selected):
+    """`selected` ids in an order that runs a prerequisite before the test
+    that names it.
+
+    Registration order otherwise, so a run reads down the page. A
+    prerequisite outside the selection places nothing: either it is
+    already satisfied, or the run that needs it will be refused and
+    recorded as skipped. validate() has ruled out cycles; the stack check
+    only keeps a malformed registry from recursing forever.
+    """
+    want = set(selected)
+    by_id = {t.id: t for t in tests}
+    out, placed = [], set()
+
+    def visit(tid, stack):
+        if tid in placed or tid not in want or tid not in by_id or tid in stack:
+            return
+        stack.add(tid)
+        for r in by_id[tid].requires:
+            visit(r, stack)
+        stack.discard(tid)
+        placed.add(tid)
+        out.append(tid)
+
+    for t in tests:
+        visit(t.id, set())
+    return out
+
+
 def validate(registry=None):
     """Every `requires` names a known test and there are no cycles."""
     reg = registry if registry is not None else REGISTRY