Format live float values to 6 significant digits matching 32-bit precision

Sox reads 32-bit floats that Python promotes to 64-bit doubles, producing
display artifacts like 22.011558532714844. Using :.6g format gives clean
values matching .sax file precision (22.0116, -19.9574, 175, 14).
Applied to both initial DOM build and COV update paths.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

device_session.py

@@ -268,7 +268,7 @@ class DeviceSession:
                 if name in sox_comp.values:
                     val = sox_comp.values[name]
                     if isinstance(val, float):
-                        val_str = f"{val:.4f}".rstrip("0").rstrip(".")
+                        val_str = f"{val:.6g}"
                     else:
                         val_str = str(val)
                     ET.SubElement(comp_elem, "prop",
@@ -365,7 +365,8 @@ class DeviceSession:
                     continue
                 name = slot["name"]
                 if name in sox_comp.values:
-                    val = str(sox_comp.values[name])
+                    raw = sox_comp.values[name]
+                    val = f"{raw:.6g}" if isinstance(raw, float) else str(raw)
                     if name in existing_props:
                         existing_props[name].set("val", val)
                     else: