Accept 0 as a feature ID in --use-attribute-for-id

strip_zeroes() removed every leading zero, so "0" became "" and never
matched std::to_string(0). The ID was rejected as too large and the
feature was left without an ID. Keep the final digit.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0172RxhnHkNgRZ3NBrsRJZYK

serial.cpp

@@ -382,7 +382,8 @@ static std::string strip_zeroes(std::string s) {
 	// Doesn't do anything special with '-' followed by leading zeros
 	// since integer IDs must be positive
 
-	while (s.size() > 0 && s[0] == '0') {
+	// Keep the final digit so that an ID of 0 compares equal to "0"
+	while (s.size() > 1 && s[0] == '0') {
 		s.erase(s.begin());
 	}