address greptile review feedback (greploop iteration 1)

- voice_caller.py: drop unused 'threading' import; make LXST/Sideband
  checkout paths overridable via LXST_SRC/SIDEBAND_SRC (SIDEBAND_SRC matches
  conftest) with a clear error if missing, instead of hardcoded ~/repos paths.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: torlando-agent[bot]

Tests/interop/voice_caller.py

@@ -12,10 +12,18 @@
   PYTHONPATH unneeded — paths injected below.
   python3 voice_caller.py <columba_identity_hex> [ring_seconds]
 """
-import sys, os, time, threading
-
-sys.path.insert(0, os.path.expanduser("~/repos/LXST"))
-sys.path.insert(0, os.path.expanduser("~/repos/Sideband"))
+import sys, os, time
+
+# LXST + Sideband are sibling checkouts; override with LXST_SRC / SIDEBAND_SRC
+# (SIDEBAND_SRC matches the interop conftest). Default to ~/repos/<name>.
+for _name, _env, _default in (
+    ("LXST", "LXST_SRC", "~/repos/LXST"),
+    ("Sideband", "SIDEBAND_SRC", "~/repos/Sideband"),
+):
+    _path = os.environ.get(_env, os.path.expanduser(_default))
+    if not os.path.isdir(_path):
+        sys.exit(f"{_name} checkout not found at {_path} — set {_env} to its path.")
+    sys.path.insert(0, _path)
 
 import RNS  # noqa: E402
 from sbapp.sideband.voice import ReticulumTelephone  # noqa: E402