# Duplicate Filename Detection

## Problem

Two files with the same filename may be ordinary copies, while names such as
`Track.mp3` and `Track 2.mp3` may indicate a OneDrive conflict. These cases need
review, but neither is sufficient evidence for deletion.

## Architecture

The duplicate detector emits immutable groups of two kinds:

- `exact_name` groups filenames after case and Unicode normalization.
- `cloud_conflict` groups names after additionally removing a trailing numeric
  suffix from the stem.

Groups contain every path, a stable comparison key, a display name, and the number
of files beyond the first. Health analysis reports exact and suspected-conflict
counts separately. Neither category changes the health score.

## Edge Cases

- Same filename in different folders.
- Case-only and Unicode representation differences.
- Multiple conflict suffixes such as `Track 2.mp3` and `Track 3.mp3`.
- Legitimate numbered titles, which remain explicitly labeled as suspected.
- A single file, which is never reported as a duplicate.

## Verification

Tests cover exact, normalized, conflict-family, unrelated, and deterministic-order
behavior, plus integration with health analysis. Detection is read-only.