fix(cpp): correct aligned all-null pages and page advancement

[ColinLeeo]

What changed

C++ serialized aligned all-null value pages with a row count, bitmap, and optional statistics and codec payload instead of the compact empty-page marker used by Java. This could cause queries to miss subsequent non-null values. A normal GORILLA page can also leave a padding byte unread after all values are decoded, preventing the C++ reader from advancing to the next page.

• Write each all-null value page as a single zero varint, without compressed size, statistics, bitmap, or codec payload.
• Handle an empty deferred first page without appending statistics or data, and recognize single-page all-null value chunks during recovery.
• Complete the aligned value page when its time rows have been consumed, clearing unread padding and decoder state before advancing.
• Refresh CLI golden file sizes and sketch offsets for the compact empty page (the all-null fixture shrinks from 457 to 451 bytes).

The final diff contains only C++ changes. Java implementations and encoding defaults are unchanged.

Validation

• C++ GTest suite with BUILD_TOOLS=ON: 1131 passed, 3 skipped (external fixture configuration unavailable), 10 disabled. The complete CTest run, including CLI and CMake tests, passed with zero failures.
• 45 parameterized read cases cover the canonical format with DICTIONARY/GORILLA, three page sizes, and record/tablet/mixed writes. Removing the reader state cleanup reproducibly fails the INT32/GORILLA case with seven rows per page; an independent codec probe confirms one padding byte remains after decoding all seven values.
• Added exact empty-page format and deferred-first-page regressions; confirmed they fail before the writer fix. Existing recovery tests pass.
• Unmodified Java read 72 newly generated C++ files successfully: 144 query checks across PLAIN, DICTIONARY, RLE, TS_2DIFF, and GORILLA, three page sizes, and record/tablet/mixed writes.
• Spotless checks for changed C++ test files and git diff --check passed.

Found while reviewing #968; the issue also reproduces without mixing record and tablet writes.

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