Slice 1 (HITL): Lance-level wrapper surface + read-path tracer bullet

Parent PRD

#7331

What to build

The foundational tracer bullet. Introduce a Lance-level wrapping surface that can decorate the store and the readers/writers it returns, then prove end-to-end observability on a path that bypasses inner today.

• Define WrappingLanceObjectStore (or equivalent) able to wrap: store-level ops, returned Reader, returned Writer. See parent §"Proposed Lance-Level Interfaces".
• Adapt the existing WrappingObjectStore so current wrappers keep working unchanged (Compatibility section).
• Route ObjectStore::open / open_with_size through the wrapper's reader hook for all schemes (local, file+uring, cloud). Local LocalObjectReader / UringReader stay specialized but are now wrapped.
• Prove it: a test wrapper counts exact get_range calls on a plain file:// path (no file-object-store://).

This is HITL: the trait shape and Open Questions 1, 4, 5 in the parent need maintainer sign-off before the surface is committed.

Acceptance criteria

• WrappingLanceObjectStore trait defined with store + reader + writer wrap hooks
• Existing WrappingObjectStore implementations continue to work (adapter or coexistence per Open Q1)
• open / open_with_size return readers passed through the wrapper for every scheme
• Test: a wrapper observes exact get_range count/byte totals on a file:// local read
• Open Questions 1, 4, 5 answered and recorded on the parent
• Existing wrapper / IO-stats tests still pass

Blocked by

None - can start immediately.

Design sections addressed

• Phase 1 (Add the Lance-Level Wrapper Surface), Phase 2 (Move Read Paths Behind Lance Readers)
• Open Questions 1, 4, 5

Start with parent PRD #7331 and Open Questions 1, 4, and 5, then trace ObjectStore::open, open_with_size, and existing WrappingObjectStore implementations. Verify completion with the file:// local-read wrapper test counting get_range calls and the existing wrapper/IO-stats tests; record the design decisions on the parent.