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.

tests/test_cli.py

@@ -207,3 +207,47 @@ def test_the_link_board_announces_itself_as_the_booths_own(tmp_path):
     m = _manifest(tmp_path / "links")
     assert m is not None and m.handle == "booth"
     assert m.why
+
+
+def test_the_flags_can_sit_on_either_side_of_the_files(tmp_path):
+    """`booth add b *.png --why "..."` and `booth add b --why "..." *.png` both
+    work. A glob is usually last and a flag usually after it, but nothing
+    enforces that and a session should not have to remember which."""
+    src = tmp_path / "a.png"
+    src.write_bytes(b"x")
+    env = {**os.environ, "ALTHING_HANDLE": "booth-dev",
+           "BOOTH_DATA_DIR": str(tmp_path), "BOOTH_URL": "http://booth.invalid"}
+    for name, args in (("after", ["add", "after", str(src), "--why", "w"]),
+                       ("before", ["add", "before", "--why", "w", str(src)])):
+        r = subprocess.run([str(SCRIPT), *args], capture_output=True, text=True,
+                           timeout=30, env=env)
+        assert r.returncode == 0, r.stderr
+        assert _manifest(tmp_path / name).why == "w"
+        assert (tmp_path / name / "a.png").exists(), "the files stopped being copied"
+
+
+def test_a_why_survives_quotes_and_non_ascii_and_is_flattened(tmp_path):
+    """The reason this goes through manifest.py instead of printf-ing JSON from
+    the shell: a why containing a quote, a backslash or a newline is not an edge
+    case, it is a sentence somebody wrote. Newlines flatten because the field
+    renders inside a card's sub-line."""
+    r = subprocess.run(
+        [str(SCRIPT), "new", "b", "--why", 'he said "pick v3" — line1\nline2 · ünï'],
+        capture_output=True, text=True, timeout=30,
+        env={**os.environ, "ALTHING_HANDLE": "booth-dev",
+             "BOOTH_DATA_DIR": str(tmp_path), "BOOTH_URL": "http://booth.invalid"})
+    assert r.returncode == 0, r.stderr
+    why = _manifest(tmp_path / "b").why
+    assert why == 'he said "pick v3" — line1 line2 · ünï'
+
+
+def test_a_flag_with_no_value_does_not_eat_the_booth_name(tmp_path):
+    """`booth new b --why` with nothing after it must not consume `b` as the
+    value and then create a booth called nothing. Usage, and no directory."""
+    r = subprocess.run([str(SCRIPT), "new", "b", "--why"], capture_output=True,
+                       text=True, timeout=30,
+                       env={**os.environ, "BOOTH_DATA_DIR": str(tmp_path),
+                            "BOOTH_URL": "http://booth.invalid"})
+    assert r.returncode == 2
+    assert "usage:" in r.stderr
+    assert not (tmp_path / "b").exists()