Filter deprecated Long Slow modem preset from picker

[mizadi]

What & why

Closes #2020.

The app still offered the deprecated LoRaConfig.ModemPreset value LONG_SLOW for new selection in the modem-preset picker. Per the upstream deprecated-fields audit this preset is being removed, and Android already filters it out. This change stops offering it for new selection while keeping full backward-compatibility for radios already configured on it.

Changes

• Added an isDeprecated flag to ModemPresets (currently just longSlow), following the same keep-the-case-but-filter pattern already used for requiresFirmware2_8.
• ModemPresets.selectable(supports2_8:) now excludes deprecated presets, so longSlow no longer appears in the LoRa config picker or the discovery scan preset list.
• Kept the longSlow case so an existing radio's value still round-trips through protobuf and renders its label.
• In LoRaConfig's availablePresets, a currently-configured deprecated preset is kept visible so the picker never shows a blank selection for an existing longSlow config.
• Added unit tests: longSlow is excluded from the selectable set (both firmware levels) and from userSelectable, and still exists for label display.

Testing

• MeshtasticTests/LoRaFirmwareGatingTests pass locally (11 tests, incl. the 2 new ones); no existing tests broken.
• SwiftLint: no new warnings vs. main.

PR Checklist

• All existing tests pass
• New tests written
• SwiftLint reports no new errors or warnings

Summary by CodeRabbit

• Bug Fixes

  • Deprecated radio presets are no longer shown as selectable options.
  • Existing setups using a deprecated preset will still display it correctly instead of appearing blank.

• Tests

  • Added coverage for deprecated preset handling and display behavior.

[CLAassistant]

All committers have signed the CLA.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 60c34254-af7b-4625-afa3-5a3474943f55

📥 Commits

Reviewing files that changed from the base of the PR and between efa3c09 and 9bb0fe0.

📒 Files selected for processing (3)

• Meshtastic/Enums/LoraConfigEnums.swift
• Meshtastic/Views/Settings/Config/LoRaConfig.swift
• MeshtasticTests/LoraDeviceEnumTests.swift

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📝 Walkthrough

Walkthrough

Introduces an isDeprecated property on ModemPresets, filters deprecated presets from selectable(supports2_8:), and updates the LoRa config picker to still display an already-configured deprecated preset (longSlow) rather than showing a blank selection. Adds corresponding tests.

Changes

Deprecate longSlow modem preset

Layer / File(s)	Summary
isDeprecated property and selectable filtering Meshtastic/Enums/LoraConfigEnums.swift	Adds isDeprecated computed property (true for longSlow) and filters deprecated presets out of selectable(supports2_8:).
Picker preserves deprecated current preset Meshtastic/Views/Settings/Config/LoRaConfig.swift	availablePresets appends the current modemPreset back into the list when it is deprecated but missing after region/support filtering, avoiding a blank picker selection.
Tests for deprecated preset behavior MeshtasticTests/LoraDeviceEnumTests.swift	Adds tests confirming longSlow is deprecated, excluded from selectable/userSelectable sets, and still round-trips correctly with the right display name.

Estimated code review effort: 2 (Simple) | ~10 minutes

Poem

A slow old preset, once picked with glee,
Now hops off the list — but stays if it's "me"!
No blank little gaps in the picker's fine row,
Just tests hopping through to make sure it's so. 🐇✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	Title clearly summarizes the main change: filtering the deprecated Long Slow modem preset from the picker.
Description check	✅ Passed	Description covers what changed, why, testing, and checklist items, matching the repository template well.
Linked Issues check	✅ Passed	Changes address #2020 by filtering longSlow from selectable presets while preserving existing-config display.
Out of Scope Changes check	✅ Passed	No clear out-of-scope changes are evident; edits stay focused on Long Slow filtering and its tests.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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_{Comment @coderabbitai help to get the list of available commands.}

[mizadi]

@thebentern The red "Check docs coverage" check is a CI/permissions issue, not a problem with this change.
The job fails on its "Post warning comment" step with: RequestError [HttpError]: Resource not accessible by integration status: 403
Because this PR is from a fork, GITHUB_TOKEN is read-only, so the workflow can't post its advisory docs-staleness comment and the step errors out. The check is advisory by design (its "Set check status" step is skipped), so the failure is purely the comment-post permission, not a code or docs problem.
All other checks (SwiftLint, tests) are green and the PR is approved. Should be good to merge whenever you're ready. Thanks!