refactor(encoding): pass mini-block compression context

[Xuanwo]

Stack 1 of the generic block compression series.

Mini-block codecs need page framing information to compare container-level choices without creating a parallel planner API. This change passes one explicit context through the existing mini-block codec tree and distinguishes ordinary mini-block pages from SparseLayout callers.

It intentionally changes no codec selection or persisted bytes: ordinary mini-block and SparseLayout writers keep their existing behavior, while later stack layers can consume the context when evaluating generic offset containers.

Validation covered the complete lance-encoding test suite and workspace clippy with warnings denied.

Stack navigation

• Umbrella / integration reference: feat(encoding): add generic block compression #8002
• Next: refactor(encoding): make block codecs fallible #8040

[codecov]

Codecov Report

❌ Patch coverage is 97.81022% with 3 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
.../lance-encoding/src/encodings/logical/primitive.rs	80.00%	0 Missing and 1 partial ⚠️
rust/lance-encoding/src/encodings/physical/fsst.rs	83.33%	0 Missing and 1 partial ⚠️
...st/lance-encoding/src/encodings/physical/packed.rs	83.33%	0 Missing and 1 partial ⚠️

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