Relax 'Maximum' buffer tier to 7GB RAM

[marcelveldt]

What does this implement/fix?

Follow-up to #4249. The Maximum buffer preset (and the auto-selected default) required exactly 8GB of RAM. Machines marketed as "8GB" frequently report a little less — integrated GPUs carve out shared system memory (e.g. a real 7.7GB), and container runtimes report their cgroup limit — so they silently dropped to the Balanced tier and never got the largest buffer.

• Lower the Maximum threshold from 8GB to 7GB, so near-8GB hosts qualify for the optimal buffer.
• Keep the 4GB Balanced minimum intact (the genuine lower bound).
• Replace the repeated magic numbers with named BALANCED_MIN_RAM_GB / MAXIMUM_MIN_RAM_GB constants and extend the buffer-tier test with the boundary cases (6.9 → Balanced, 7.0 / 7.7 → Maximum).

Related issue (if applicable):

• n/a

Types of changes

• Bugfix (non-breaking change which fixes an issue) — bugfix
• New feature (non-breaking change which adds functionality) — new-feature
• Enhancement to an existing feature — enhancement
• New music/player/metadata/plugin provider — new-provider
• Breaking change (fix or feature that would cause existing functionality to not work as expected) — breaking-change
• Refactor (no behaviour change) — refactor
• Documentation only — documentation
• Maintenance / chore — maintenance
• CI / workflow change — ci
• Dependencies bump — dependencies

Checklist

• The code change is tested and works locally.
• pre-commit run --all-files passes.
• pytest passes, and tests have been added/updated under tests/ where applicable.
• For changes to shared models, the companion PR in music-assistant/models is linked.
• For changes affecting the UI, the companion PR in music-assistant/frontend is linked.
• I have read and complied with the project's AI Policy for any AI-assisted contributions.
• I have raised a PR against the documentation repository targeting the main or beta branch as appropriate.

[Copilot]

Pull request overview

This PR adjusts the Streams controller’s RAM-gated buffer preset thresholds so that hosts reporting slightly under “8GB” (e.g., due to shared GPU memory or cgroup limits) still qualify for the Maximum buffer tier, and it updates the related tests and inline documentation accordingly.

Changes:

• Lower the Minimum RAM threshold for Maximum buffer preset from 8GB to 7GB.
• Introduce named constants (BALANCED_MIN_RAM_GB, MAXIMUM_MIN_RAM_GB) to replace repeated magic numbers.
• Extend the buffer-size gating tests with boundary cases around the new 7GB cutoff.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
music_assistant/controllers/streams/constants.py	Adds RAM threshold constants and applies the new 7GB cutoff to available presets and default selection logic.
music_assistant/controllers/streams/controller.py	Updates the config-entry comment to reflect the new Maximum RAM threshold.
tests/controllers/streams/test_buffer_size.py	Adds new boundary test cases validating the updated RAM gating behavior for available buffer presets.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.