Live Editor: add DASP/Sox device connection with full CRUD and COV

Port the DASP transport and Sox protocol stack from sedonaOntrol Java
to Python, enabling live device editing alongside the existing offline
SAX editor. Lazy-loads components on navigation, caches them, and
subscribes to COV events for the active wiresheet.

New files: dasp.py, sox.py, device_session.py, connect_dialog.py,
live_hooks.py. Modified: app_state.py (live-mode state), main.py
(Device menu, COV polling, lazy tree expand), properties.py (Sox
write-through), sax_file.py (structural mutations route through
live_hooks), schema.py (find_manifest helper).

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

schema.py

@@ -224,6 +224,18 @@ def find_manifest_path(kit_name, checksum):
     return None
 
 
+def find_manifest(kit_name, checksum):
+    """Returns the parsed ET root of a kit manifest, or None."""
+    checksum_hex = f"{checksum:08x}" if isinstance(checksum, int) else checksum
+    path = find_manifest_path(kit_name, checksum_hex)
+    if path is None:
+        return None
+    try:
+        return ET.parse(path).getroot()
+    except Exception:
+        return None
+
+
 def load_schema_kits_and_manifests():
     """Loads the manifests for the file's <schema> kits, plus any kit still only pending.