Fix hyphenated issue prefix detection (#199)

- update prefix/number parsing to use the last hyphen across utils and nodb paths
- add regression tests covering multi-hyphen prefixes in both packages

cmd/bd/nodb.go

@@ -173,11 +173,11 @@ func detectPrefix(beadsDir string, memStore *memory.MemoryStorage) (string, erro
 
 // extractIssuePrefix extracts the prefix from an issue ID like "bd-123" -> "bd"
 func extractIssuePrefix(issueID string) string {
-	parts := strings.SplitN(issueID, "-", 2)
-	if len(parts) < 2 {
+	idx := strings.LastIndex(issueID, "-")
+	if idx <= 0 {
 		return ""
 	}
-	return parts[0]
+	return issueID[:idx]
 }
 
 // writeIssuesToJSONL writes all issues from memory storage to JSONL file atomically

cmd/bd/nodb_test.go

@@ -18,6 +18,7 @@ func TestExtractIssuePrefix(t *testing.T) {
 		{"standard ID", "bd-123", "bd"},
 		{"custom prefix", "myproject-456", "myproject"},
 		{"hash ID", "bd-abc123def", "bd"},
+		{"hyphenated prefix", "alpha-beta-1", "alpha-beta"},
 		{"no hyphen", "nohyphen", ""},
 		{"empty", "", ""},
 	}