docs: document the full-mix-vs-stems auto-switch in the Stem Mixer

[topkoa]

Follow-up to the Stem Splitter page. Two changes, both verified against the code.

The behavior (confirmed in plugins/stems/src/mix-gains.js)

computeMixGains plays the song's pristine full mix — the original audio, not a recombination of the separated stems — whenever a full mix exists and every stem is on at 100% ("unity"). The instant any stem is muted or lowered, it crosses to the separated stems, and stays there until every stem is back at 100%.

The point is quality: separation is lossy, so summing stems back isn't identical to the original. Playing the real full mix by default means you only pay that cost when you actually want a custom balance.

Docs

• Stem Mixer page — new "Full Mix vs. Separated Stems" section stating the rule and why it exists, plus the note that a song with no full mix simply always plays the stems.
• Stem Splitter page — the "use it when you need the untouched audio" note now links to the mixer and explains it's automatic (you hear the untouched audio until you change the balance).
• Added the Stem Splitter cross-link to the mixer's Related Pages.

Builds clean under mkdocs build --strict.

Summary by CodeRabbit

• Documentation
  • Clarified that the original full mix is always retained alongside separated stems.
  • Explained that playback uses the untouched mix until stem levels are adjusted.
  • Expanded guidance on when playback switches between full mix and separated stems, including related quality caveats.
  • Added a related link to the Stem Splitter documentation.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

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Run ID: 2b2e9a9a-2ead-4232-aa4f-935ea22bf47d

📥 Commits

Reviewing files that changed from the base of the PR and between f0dcec3 and 956f6de.

📒 Files selected for processing (1)

• docs/plugins/stems.md

🚧 Files skipped from review as they are similar to previous changes (1)

• docs/plugins/stems.md

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📝 Walkthrough

Walkthrough

Updated Stem Mixer documentation to explain full-mix and separated-stem playback behavior, clarified the Stem Splitter losslessness caveat, and added a related-page link.

Changes

Stem Mixer documentation

Layer / File(s)	Summary
Playback behavior and cross-links docs/plugins/stems.md, docs/plugins/stem-splitter.md	Documents automatic full-mix playback at unchanged stem levels, switching to separated stems when levels change, lossiness considerations, full-mix fallback behavior, and the Stem Splitter related-page link.

Estimated code review effort: 1 (Trivial) | ~3 minutes

Possibly related PRs

• got-feedBack/feedBack-user-guide#5: Added Stem Splitter documentation and related-page guidance updated here.
• got-feedBack/feedBack-user-guide#7: Updated the same lossless-separation guidance in the Stem Splitter documentation.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main docs change: documenting the Stem Mixer’s automatic switch between full mix and separated stems.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch docs/stems-mixer-full-mix

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