[TASK] RemovalLogger actor + JSONL append path

[kirich1409]

Context

Actor-isolated single writer to ~/.local/state/devsweep/removed.jsonl. Month-boundary rotation + 100 MB fallback. Permissions 0600.

Acceptance criteria

• Actor with record(entry) API.
• Rotation atomic (temp + rename + fsync).
• File mode 0600.

Files to touch (estimate)

best-effort estimate; agent refines during implementation

Implementation notes

n/a

Dependencies

• Blocked by [TASK] FileSystem protocol + FileSystemImpl #38

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