feat: add BaseLanceNamespace that provides an implementation of all APIs through the Lance Java SDK

[wombatu-kun]

Closes #169

Summary

Add BaseLanceNamespace — a filesystem-directory-based implementation of the LanceNamespace interface that delegates table operations to the Lance Java SDK (lance-core).

New module: lance-namespace-base

Key implementation details

• Arrow IPC for data serialization across the interface boundary
• Symlinks for registerTable -- references external datasets without copying
• Cursor-based pagination on all list operations (limit + pageToken using sorted cursor tokens for string lists, simple limit truncation for object lists)
• Vector search parameters: k, nprobes, ef, refineFactor, distanceType, bypassVectorIndex (mapped to SDK's setUseIndex(false))
• Full-text search: single-column match and multi-column multiMatch
• Merge insert: supports whenMatchedUpdateAll (with optional filter), whenNotMatchedInsertAll, whenNotMatchedBySourceDelete (with optional filter)
• Scalar index types: BTREE, BITMAP, INVERTED/FTS; default IVF_PQ for vector indexes
• Tag error detection: heuristic string-matching on SDK exceptions (documented as fragile)
• Storage options: storage.* config prefix passed through to all Dataset operations, enabling cloud backends

Known limitations

• fastSearch, lowerBound, upperBound query parameters are not forwarded (no SDK support in lance-core 5.0.0-beta.1)
• pageToken on listTableVersions, listTableTags, listTableIndices is not supported (only limit truncation)
• Tag-not-found detection relies on SDK error message string matching

[github-actions]

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