[TASK] RemovalLogger fsync-count benchmark (AC-31)

[kirich1409]

Context

Drive RemovalLogger through 200 items and count fsync syscalls.

Acceptance criteria

• AC-31 passes.

Files to touch (estimate)

best-effort estimate; agent refines during implementation

Implementation notes

n/a

Dependencies

• Blocked by [TASK] Batched fsync implementation (P3) #52
• Blocked by [SPIKE] benchmark framework choice #88

Safety checklist

See .github/ISSUE_TEMPLATE/task.yml — tick applicable invariants in the issue if any destructive path is touched.

Definition of Done

• Acceptance criteria satisfied and verifiable
• Tests added or updated
• No build / lint / test regressions
• Self-review against research-report invariants
• Code review approved