[#60] Complete JPMS runtime compatibility through Java 25

[peter-lawrey]

Strengthen the named-module runtime checks from #60 while preserving the direct-buffer fast path. The integer-array oracle now compares hashing against an explicitly native-order byte representation instead of accepting any nonzero result. Keep the existing heap/direct-buffer equivalence, offsets, cursor checks and packaged-stub exclusion tests.

Apply the Actions setup repair already validated in #120: current checkout/cache/Java actions and a Java 21 scanner runtime. Hashing output and the Java 8 library target are unchanged. SonarCloud authentication remains a separate external gate; analysis is still enabled.

Packaging is inherited from #122 at 41381de5878f5ad8ec62f20a8f48163073f49632, whose current target is develop. Review that explicit-module packaging first, then retarget this PR after #122 merges.

Fresh evidence on Linux amd64:

• Java 8, Java 21 and Java 25 Maven clean verify passed. Java 8 ran 14,901 unit tests with 12 existing skips; Java 21 and Java 25 each ran two string configurations with 14,901 tests each and 5/8 existing skips. All had zero failures/errors. Packaged-JAR checks and the class-path consumer passed; the named-module consumer passed on Java 21 and Java 25 and is intentionally skipped on Java 8.
• One fresh Java-8-built JAR was retained unchanged and identified by SHA-256 aebb1f24e5d1b5cc747b806c2827b6a9da3899fea7d0774e8dd70d20c28145ae.
• That same JAR passed class-path execution on Java 8/11/17/21/25 and explicit-module execution on Java 11/17/21/25. The consumer exercised all 25 public scalar/tuple factory overloads, both buffer byte orders, direct-buffer offsets/cursors and scalar primitive-array equivalence. All nine launches produced checksum -7613445165642694420.
• Java 25 launches without the required export failed with IllegalAccessError in both deployment forms. The required flags remain --add-exports java.base/sun.nio.ch=net.openhft.hashing for modules and --add-exports java.base/sun.nio.ch=ALL-UNNAMED for the class path.
• The retained JAR has Java 8 class version 52, an explicit descriptor at META-INF/versions/9/module-info.class, a Multi-Release manifest and no sun/nio/ch/DirectBuffer.class. jar --validate and module-description checks passed.
• Actionlint passed. Actions run 34603804160 on this head passed checkout, Java setup, both caches and the test/build phases, then failed SonarCloud analysis with "Not authorized or project not found". The token/project configuration needs administrator disposition; CI is not green. Commands, logs, source and binary provenance are retained in the local follow-up evidence pack.

The older claimed JAR with digest a468b81e3956b6da43376a6620e83a791bedddfb57cfb6250410958ece50361e could not be recovered from its recorded path or 58 local candidate JARs. The fresh results above replace the unsupported historical matrix claim; they do not verify that older binary. They also do not establish other-platform CI success or full algorithm conformance beyond the submitted regression suite and stated runtime checks.

Refs #60.