feat(lora): honor a pinned-preset intent advertised for UNSET

[jamesarich]

Why

Second half of #6704 (stacked on the placeholder-gate PR).

The placeholder heuristic in the previous PR can't tell a vendor build that deliberately pins LONG_FAST from a stock install: both report region UNSET + LONG_FAST. meshtastic/firmware#11507 closes that gap by advertising an UNSET entry in LoRaRegionPresetMap when, and only when, the build pins a preset, stating the pin as the group's sole entry and default.

What changed

🌟 presetForRegionChange() now treats a non-null constraintFor(RegionCode.UNSET) as an explicit statement that the current preset is deliberate: fresh setup keeps it (legality-repaired only), even when it is LONG_FAST. Firmware that sends no UNSET entry (stock builds, and everything shipped today) falls through to the placeholder heuristic unchanged.

Notes for reviewers

• The UNSET lookup is scoped to the fresh-setup decision only: the picker's constraint lookup now explicitly skips UNSET, so a pinned build's single-entry group never collapses the dropdown while the region is still unset — matching #11507's "intent, not enforcement", and confirmed as the intended reading by the map's author on Fresh-setup preset default overwrites a preset that is still legal in the chosen region #6704. Behavior-neutral on firmware without the entry (constraintFor(UNSET) was null there anyway).
• Inert on today's firmware: no shipped release emits an UNSET entry, so behavior is identical to the previous PR until firmware#11507 lands.

Testing Performed

• :core:model:allTests — new tests: a map with an UNSET entry keeps a pinned LONG_FAST at fresh setup; the same pin is still legality-repaired when illegal in the chosen region; maps without an UNSET entry keep the placeholder heuristic.
• :feature:settings:allTests, spotlessCheck, detekt, kmpSmokeCompile — green.

Summary by CodeRabbit

• Bug Fixes
  • Preserves deliberately selected radio presets during fresh setup, including LONG_FAST.
  • Repairs presets when they are not valid for the selected region.
  • Keeps preset selection unrestricted while the region remains unset.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: 68faf186-a264-4a68-bbc1-ca576f1b654b

📥 Commits

Reviewing files that changed from the base of the PR and between 809af8d and fe46acf.

📒 Files selected for processing (3)

• core/model/src/commonMain/kotlin/org/meshtastic/core/model/RegionPresetConstraint.kt
• core/model/src/commonTest/kotlin/org/meshtastic/core/model/LoRaRegionPresetsTest.kt
• feature/settings/src/commonMain/kotlin/org/meshtastic/feature/settings/radio/component/LoRaConfigItemList.kt

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📝 Walkthrough

Walkthrough

The change adds explicit handling for firmware-advertised UNSET preset constraints. Fresh setup preserves deliberate pins, invalid pins are repaired for concrete regions, and the settings picker remains unconstrained while the region is UNSET.

Changes

UNSET preset handling

Layer / File(s)	Summary
Model preset preservation and validation core/model/src/commonMain/kotlin/org/meshtastic/core/model/RegionPresetConstraint.kt, core/model/src/commonTest/kotlin/org/meshtastic/core/model/LoRaRegionPresetsTest.kt	The model preserves a LONG_FAST pin when an explicit UNSET constraint exists. Tests verify that illegal pins are still repaired for UA_433.
Settings picker constraints feature/settings/src/commonMain/kotlin/org/meshtastic/feature/settings/radio/component/LoRaConfigItemList.kt	The picker skips constraint lookup for UNSET and continues using mapped constraints for concrete regions.

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

Merge Risk: ⚪ Minimal · up to fe46a

The PR narrowly changes fresh-setup preset selection for firmware that explicitly advertises a pinned preset while preserving existing behavior otherwise; no actionable merge-blocking risk remains after normal checks and review.

Possibly related issues

• meshtastic/firmware#11506 — Covers client handling of firmware UNSET constraints to preserve pinned modem presets.
• meshtastic/Meshtastic-Android#6704 — Tracks UNSET constraint handling during fresh setup.
• meshtastic/Meshtastic-Apple#2273 — Addresses equivalent preservation of modem presets advertised through UNSET.

Possibly related PRs

• meshtastic/Meshtastic-Android#6710 — Extends related presetForRegionChange logic and tests for UNSET pins.

Suggested labels: bugfix

🚥 Pre-merge checks | ✅ 6 | ❌ 2

❌ Failed checks (1 warning, 1 inconclusive)

Check name	Status	Explanation	Resolution
Regression Coverage For Changed Behavior	⚠️ Warning	LoRaRegionPresetsTest covers the model helper, but no settings test covers LoRaConfigScreen's UNSET picker branch; a pinned UNSET map could still collapse the dropdown.	Add a Compose or extracted-helper test with a 2.8-capable pinned map: at UNSET expose presets outside the UNSET group, then verify a concrete region applies its constraint.
Tests Prove The Path, Not The End State	❓ Inconclusive	I need to inspect the full test history and the covered production path before deciding whether the added assertions can pass after a revert.	Determine whether each changed test fails against the pre-PR implementation or only checks returned state without distinguishing the intended path.

✅ Passed checks (6 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: honoring pinned-preset intent advertised through an UNSET entry.
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.
Sibling Call Sites And Presence Semantics	✅ Passed	The diff only adds UNSET constraint presence handling; all production constraintFor uses are covered by the model helper and picker, with no changed physical-value field or new zero default.
Moved Code Diffed Against Its Original	✅ Passed	The region-change block is extracted to presetForRegionChange with one migrated caller; no listed override, validation, default, nullability, annotation, or coroutine-policy change appears in the d...

✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

• Create stacked PR
• Commit on current branch

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[jamesarich]

@coderabbitai full review

[coderabbitai]

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