Media: Only count attachments from the mirrored query collection

[itzmekhokan]

Fixes the Media Library tab reporting "Showing 1 of 2 media items" after uploading the first image into an empty library through the Featured Image modal.

What the problem was:

• wp.media.model.Attachments.observe() bound the total-attachments counters (_addToTotalAttachments/_removeFromTotalAttachments) to every observed collection.
• The Featured Image state additionally observes the selection (library.observe( this.get('selection') )). With autoSelect, an uploaded image is added both to the mirrored query and to the selection, so it was counted twice — total became 2 for a single item.

What the fix does:

• Restricts the total-count handlers to the mirrored query collection, so the count reflects only the items in the library itself.
• Also corrects two JSDoc issues in the touched code (a missing @param name on observe() and a copy/paste description on _removeFromTotalAttachments()).

Approach and why:

• The count is meant to track the library (query) total. Other observed collections such as the selection should never change it; gating the bindings on attachments === this.mirroring is the minimal, correct expression of that intent and also resolves the same latent double-count in replace-image, gallery-edit, and collection-edit.

Trac ticket: https://core.trac.wordpress.org/ticket/65513

Use of AI Tools

AI assistance: Yes
Tool(s): Claude Code
Model(s): Claude Opus 4.8
Used for: Ticket analysis, live reproduction, root-cause investigation and verification. All changes were reviewed, validated against the codebase, and are taken responsibility for by me (Khokan Sardar).

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[github-actions]

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