Add ALP-RD to the cascade competition (#304)

[dfa1]

What

AlpRdEncodingEncoder was registered on WriteRegistry but never added to the top-level cascade codec list, so it could only appear as a child encoding — never be selected for an F64/F32 column. High-precision floats that plain ALP can't fit without an exception on nearly every row fell back to raw vortex.primitive (or dict), while the Rust reference uses vortex.alprd.

Encoding tree for nyc-311 Latitude:

vortex-jni Latitude:   vortex.alprd          vortex-java Latitude (before):  vortex.primitive  ❌ RAW
vortex-jni Longitude:  vortex.alp            vortex-java Longitude:          vortex.alp  ✅ (plain ALP fits)

How

Add AlpRdEncodingEncoder to the cascade competition next to AlpEncodingEncoder. It competes on measured size, so it only wins where it's actually smaller: Latitude flips to alprd, Longitude keeps plain alp. No wire/reader change — alprd is already decodable (the reader reads Rust files that use it; the 217-test interop suite confirms).

Impact (real nyc-311 corpus)

	vortex-java	vs vortex-jni (1762 MB)
Before (main)	1678.86 MB	0.95×
After	1644.25 MB	0.93×

−34.6 MB — java is now 118 MB under the Rust reference on nyc-311.

Testing

• New integration test: a high-precision F64 column (tight range, random mantissas) selects vortex.alprd via the cascade and round-trips.
• 217 Java-writes-Rust-reads interop tests pass; full ./mvnw verify green.

Closes #304.