fix: Set COLUMNS/LINES env vars without TERM=dumb

Previous fix with TERM=dumb caused Public channel to disappear.
Only setting COLUMNS and LINES as fallback for os.get_terminal_size().

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

meshcore-bridge/bridge.py

@@ -90,11 +90,10 @@ class MeshCLISession:
         logger.info(f"Starting meshcli session on {self.serial_port}")
 
         try:
-            # Set terminal size env vars for meshcli (prevents os.get_terminal_size() errors)
+            # Set terminal size env vars for meshcli (fallback for os.get_terminal_size())
             env = os.environ.copy()
             env['COLUMNS'] = '120'
             env['LINES'] = '40'
-            env['TERM'] = 'dumb'
 
             self.process = subprocess.Popen(
                 ['meshcli', '-s', self.serial_port],