Fix get_active_document_info to return actual layer data

[bbible3]

This PR fixes get_active_document_info so it returns real layer information instead of always returning empty layers and layer_sets arrays.

What changed

• Added layer extraction from the active Photoshop document via the DOM API (doc.artLayers).
• Added layer set extraction via doc.layerSets.
• Kept existing Action Manager-based document metadata logic intact.
• Excluded background layer from the returned layers list so the count matches visible/user content layers in typical workflows.

Why

The session tool get_active_document_info was reporting zero layers even when layers existed in the active document, which made layer-related diagnostics and automation unreliable.

Validation

• Before fix: MCP response returned empty layers on a document known to contain layers.
• After fix: MCP response correctly returned the layer list and count (validated against an active document with expected layers).

Notes

• This change is scoped to active document info reporting only.
• No behavior changes to document creation/editing tools.