Java 25's Compact Object Headers: I Measured the Real Savings So You Don't Have To

JEP 519 shrinks every Java object's header from 12 bytes to 8 in JDK 25. I ran real benchmarks on JDK 25.0.3 (not borrowed numbers) to measure the actual per-object savings for a realistic Spring Boot DTO shape, and explain why my numbers don't match the JEP's own headline figure.