docs(smart-playlists): document album-level fields

[deluan]

Description

Documents the five album-level smart playlist fields shipped in navidrome/navidrome#5899: albumdateadded, albumdatemodified, albumduration, albumsongcount and albumsize.

Three changes to content/en/docs/usage/features/smart-playlists/index.md:

• Fields table — five new rows alongside the existing album* entries.
• Example 8 — a worked example for the use case that motivated the feature: recently added albums that still play in album order. Sorting by the track-level dateadded scatters an album's tracks because each track has its own timestamp; albumdateadded keeps them together.
• Notes — albumduration, albumsongcount and albumsize added to the list of fields supporting numeric comparisons, and the "Album & Artist Fields" note now distinguishes these album-describing fields from the listening-history ones, since being identical across an album is exactly what makes them useful as a sort key.

The example carries a caveat worth flagging for review: an album's date added is the oldest file creation date among its tracks, so a bulk copy or restore can leave many albums with an identical timestamp. When albums tie, the following sort fields (discnumber, tracknumber) apply across all the tied albums and interleave their tracks. Adding album as a tiebreaker fixes it, which is why the example uses -albumdateadded,album,discnumber,tracknumber rather than the shorter form. This was raised in review on the Navidrome PR and deliberately documented rather than fixed in code — injecting a sort key automatically would override user-specified sort semantics and would have to change the existing album* fields to stay consistent.

Type of change

• App catalog entry (new app or update) — fill in the section below
• Documentation
• Bug fix
• Styling / layout
• Other

Checklist

• Internal links use Hugo's relref shortcode
• I previewed my changes locally (npm start) when relevant
• The build passes (npm run build)

The only new link is a same-page anchor to Example 8, which follows the existing convention in this file (e.g. the MusicBrainz fields cross-reference) rather than relref, since relref targets other pages. Verified in the built output that the table rows, the anchor and the alert shortcode all render.

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: eb4b7cd0d7

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".