fix(vis): only strip Quantity for plain (non-pint) format specs

The previous fix stripped magnitudes from every Quantity in leg_dat, but
the default-spec branch in WaveformBrowser.__init__ substitutes
'0.3gP~' for entries without an explicit format. Stripping there made
the format call ValueError out because '0.3gP~' is invalid for plain
floats.

Parse each legend format string and only strip Quantities whose spec
has no pint formatter character (~, P, H, L, C, D). Default '0.3gP~'
and explicit pint specs keep the Quantity; user-provided plain specs
like '0.1f' get the magnitude so pint's DeprecationWarning does not
fire.

Also add tests/test_units.py to lock in the application-registry
sharing contract (importing dspeed must not replace pint's app
registry, and consumer-created quantities must interoperate with
dspeed.units.unit_registry quantities).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: gipert

src/dspeed/vis/waveform_browser.py

@@ -549,9 +549,14 @@ def draw_current(self, clear: bool = True) -> None:
                     leg_labels.append(form)
         else:
             for form in self.legend_format:
+                plain_names = {
+                    name
+                    for _, name, spec, _ in string.Formatter().parse(form)
+                    if name and spec and not (set(spec) & set("~PHLCD"))
+                }
                 for leg_dat in leg_cycle:
                     leg_dat = {
-                        k: v.m if isinstance(v, Quantity) else v
+                        k: v.m if k in plain_names and isinstance(v, Quantity) else v
                         for k, v in leg_dat.items()
                     }
                     leg_labels.append(form.format(**leg_dat))

tests/test_units.py

@@ -0,0 +1,15 @@
+import pint
+
+
+def test_shares_application_registry():
+    # Importing dspeed.units must not replace the application registry, and
+    # quantities created via the bare pint API must interoperate with dspeed's
+    # registry (regression for cross-registry errors in consumer code).
+    app_reg_before = pint.get_application_registry()
+    from dspeed.units import unit_registry as ureg
+
+    assert pint.get_application_registry() is app_reg_before
+
+    consumer_q = pint.Quantity(1, "us")
+    dspeed_q = ureg.Quantity(1000, "ns")
+    assert (consumer_q + dspeed_q).to("us").magnitude == 2