test(probe): teach the layout probe about <details>, and guard the flag parser

THE PROBE. A control inside a CLOSED <details> is laid out but sits
outside its collapsed parent's box, so elementFromPoint at its centre
returns an ancestor and it reports OCCLUDED — 23 of them on sindra-set,
every one a false positive. Verified both ways before believing it:
closed, elementFromPoint returns div.gallery; opened, the button itself,
and a real trial click lands on it.

Opening every <details> rather than skipping them is the deliberate
choice. Skipping would make the probe quiet by declaring put-away
controls out of scope, and the add-note button inside
details.item-addnote is exactly the class of control this instrument
exists to check. Fourth false-positive class this probe has grown a
guard for; the other three are already in its header.

THE FLAG PARSER. Three cases that silently break and are cheap to
pin: the flags on either side of the glob (a session should not have to
remember which), a why carrying quotes, an em-dash, a newline and
non-ASCII, and --why with no value after it, which must produce usage
rather than eating the booth name and creating a booth called nothing.

313 tests.

scripts/layout-probe.py

@@ -69,6 +69,24 @@ def probe(page, url: str) -> list[str]:
             card.hover(timeout=1500)
         except Exception:
             pass
+    # ⚠ OPEN EVERY <details> FIRST. A control inside a CLOSED one is laid out
+    # but sits outside its collapsed parent's box, so `elementFromPoint` at its
+    # centre returns an ancestor and it reports OCCLUDED — 23 of them on
+    # `sindra-set`, every one a false positive, because the only way an operator
+    # reaches that button is by opening the disclosure first. Verified both
+    # ways: closed -> elementFromPoint returns div.gallery; opened -> the button
+    # itself, and a real trial click lands on it.
+    #
+    # Opening rather than SKIPPING is deliberate. Skipping would make the probe
+    # quiet by declaring put-away controls out of scope, and the add-note button
+    # inside `details.item-addnote` is exactly the kind of control this
+    # instrument exists to check. Open it and ask the real question.
+    for d in page.locator("details:not([open])").all():
+        try:
+            d.evaluate("(el) => el.open = true")
+        except Exception:
+            pass
+    page.wait_for_timeout(150)
     for el in page.locator("button, a.dl-link, a.thumb").all():
         try:
             # ⚠ elementFromPoint is VIEWPORT-relative. Without scrolling first,