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

[wjones127]

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 Slice 1 (HITL): Lance-level wrapper surface + read-path tracer bullet #7332
• Blocked by Slice 2: Write-path through wrapped Lance Writer #7333

Design sections addressed

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