Preserve distinct same-name skills across paths and projects

[Railly]

Context

The scanner first deduplicates true replicas by real-path-derived ID, then collapses every repeated display name into the first item. The second path and content are discarded while its tool ID is attached to the first item.

Evidence:

• src/scanner.ts:303-329 performs name-only collapsing.
• src/types.ts:27-30 stores only one path and one content value per item.

This hides unrelated project skills and divergent per-agent copies that happen to share a name. Editing the visible item affects only the first file while the UI implies broader ownership.

Task

Deduplicate only identical real paths or model same-name files as a replica group retaining every path, tool, project, and content identity.

Acceptance criteria

• The same real file discovered through multiple tools remains one item with combined attribution.
• Different files with the same name remain individually addressable or retain every replica.
• Edit and delete operations target an explicit path.
• Favorites, collections, counts, and project filters remain stable.
• Fixture tests cover same-name collisions and divergent copies.