chore(index): remove dead eager FM-index queries

[Xuanwo]

The production query path has moved to LazyFMIndex, but the build-time FMIndex still retained an eager query implementation used only as a test oracle. Maintaining both paths increased maintenance cost and left dead code hidden behind #[allow(dead_code)].

This removes the eager RankBitVec, HuffmanWaveletTree, and FMIndex query methods and their oracle-only tests. The FM-index builder, suffix-array sampling, serialization, and lazy production query path remain unchanged.

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📥 Commits

Reviewing files that changed from the base of the PR and between aea6ded and b91901b.

📒 Files selected for processing (1)

• rust/lance-index/src/scalar/fmindex.rs

💤 Files with no reviewable changes (1)

• rust/lance-index/src/scalar/fmindex.rs

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📝 Walkthrough

Walkthrough

The change removes non-lazy rank, wavelet-tree query, and in-memory FMIndex search and locate operations. Related search and query-consistency tests are deleted or reduced, while index construction and serialization remain.

Changes

FMIndex query path removal

Layer / File(s)	Summary
Remove rank and wavelet query primitives rust/lance-index/src/scalar/fmindex.rs	RankBitVec no longer exposes bit/rank queries, and HuffmanWaveletTree no longer exposes access or rank operations.
Remove FMIndex search implementation and coverage rust/lance-index/src/scalar/fmindex.rs	FMIndex substring search and locate helpers are removed, along with tests covering search, locate, sentinel handling, and wavelet query consistency.

Estimated code review effort: 3 (Moderate) | ~20 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main change: removal of dead eager FM-index query code.
Description check	✅ Passed	The description matches the changeset and explains the removed query paths and tests while noting what remains unchanged.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

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• Create PR with unit tests
• Commit unit tests in branch xuanwo/remove-dead-fmindex-query

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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