[CPP] Apply residual row offsets in non-aligned page decoding

[ColinLeeo]

Non-aligned prepared reads skip whole chunks and pages using statistics, but previously left any remaining row offset unapplied during page decoding. For a tree series containing values 0..39, an indexed series[30:40] returned 0..9 instead of 30..39.

Consume the residual offset after filtering in the boolean, string, and numeric batch decoders, while retaining whole-chunk/page skipping. Continue scanning after a page whose matching rows were consumed by the offset, and preserve the counter when decoding resumes on an unfinished page.

Regression coverage includes six value types, small output capacities, page/chunk boundaries, pages larger than the output block, filtered offsets, exhausted ranges, and Python slices across files and reopened indexes.

Validation:

• C++ reader/query suites: 121 passed (7 existing disabled tests excluded), with Snappy and LZ4 enabled.
• Full Python suite: 527 passed, 1 skipped.
• Changed C++ lines checked with clang-format; Python checked with Black; git diff --check passed.