[ColinLeeo]

Summary

Closes #1057.

The Java/C++ compatibility matrix now covers every (type, encoding, compression)
combination both implementations can write, at four data scales, in both
directions — and building it out surfaced and fixed two real cross-language
format bugs.

Changes

• Add a shared spec (compat/compatibility-matrix.csv) consumed by both the
  Java and C++ tests, so the two matrices cannot drift.
• Replace the table-only Java/C++ compatibility tests with a single
  spec-driven EncodingCompressionCompatibilityTest on each side, covering
  both models (table + tree), all six compressions, and four data scales
  (10 / 1k / 100k / 1M rows) with page sizes that cross page boundaries at
  every scale.
• Implement the C++ codecs that were missing so every Java-writable
  combination is now C++-readable: FLOAT/DOUBLE RLE, FLOAT/DOUBLE GORILLA_V1,
  DATE/TIMESTAMP ZIGZAG/SPRINTZ, BOOLEAN RLE.
• Fix two cross-language format bugs found by the expanded matrix:
  • INT64 RLE run values were read little-endian in C++ but written
    big-endian by Java/IoTDB.
  • The SPRINTZ FIR predictor used a 128-bit intermediate in C++, diverging
    from Java's 32/64-bit wrapping multiply on large values.
• Narrow the compatibility workflow trigger to the binary-format surface
  (main source, the spec, build files) so routine PRs don't pay the ~30 minute
  matrix; the coverage/self-check tests still run in the normal unit suite.
• Report the per-run coverage/gap matrix in the CI job summaries.

Validation

• Java generates 3260 fixtures; C++ reads all 3260 (0 skipped).
• C++ generates 3168 fixtures; Java reads all 3168.
• C++ full unit suite: 1421 passed, 0 failed.
• Java encoding/RLE/SPRINTZ tests pass; spotless:check clean.