[TASK] FileSystem protocol + FileSystemImpl

[kirich1409]

Context

Public FileSystem exposes read-only ops. Impl in DevsweepCorePrivate wraps FileManager. Public surface has NO removeItem / trashItem.

Acceptance criteria

• Protocol methods: enumerate, stat, canonicalize, attributes.
• Impl uses getattrlistbulk for bulk metadata reads where possible (foreshadows P1).
• No destructive ops in public protocol.

Files to touch (estimate)

best-effort estimate; agent refines during implementation

Implementation notes

n/a

Dependencies

None.

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