Slice 3: Reimplement IO stats as a pure store/reader/writer wrapper

Parent PRD

#7331

What to build

Convert IO statistics into an ordinary Lance-level wrapper around the store, Reader, and Writer. Remove the bespoke local compensation: LocalObjectReader / UringReader / LocalWriter should no longer call IOTracker::record_read / record_write directly — stats come from the wrapped reader/writer counting the actual ranges Lance reads and writes.

Acceptance criteria

• IOTracker reimplemented as a WrappingLanceObjectStore wrapping store + reader + writer
• No record_read / record_write calls remain in local.rs / uring/* / object_writer.rs
• Stats count exact ranges read from an opened local file (not just the initial open)
• Existing IO-stats tests pass; add a local-read range-count assertion
• Parity: local and cloud stats produced by the same mechanism

Blocked by

• Blocked by #7332
• Blocked by #7333

Design sections addressed

• "Accurate I/O Statistics"; Success criterion #2

First resolve or review blockers #7332 and #7333, then inspect local.rs, uring/*, and object_writer.rs along with the existing IO-stats tests. Verify how the store, Reader, and Writer can be wrapped without direct record_read or record_write calls. Done means exact local-file ranges are counted, local and cloud stats share the mechanism, and the existing tests plus a local-read range assertion pass.