fix: align channel QR share contract

[RCGV1]

Summary

• Default channel QR sharing to Replace.
• Serialize an explicit Add URL from a ChannelSet without lora_config, while retaining ?add=true.
• Cover raw-payload and parser round trips for Replace and Add across all supported channel counts (1-8).
• Bind the screen's initial share state to the URL passed to QrDialog, with a focused Replace-flow regression test.

Deliberately Out Of Scope

This is the first focused contract change only. Channel-capacity and duplicate conflict UX, a unified intake/share workflow, system share or deep-link entry points, and reboot/resync handling remain tracked in #6324.

Validation

:core:model:jvmTest :feature:settings:jvmTest \
  --tests org.meshtastic.core.model.util.ChannelSetUrlTest \
  --tests org.meshtastic.feature.settings.radio.channel.ChannelScreenTest \
  spotlessCheck detekt

Passed locally with Homebrew OpenJDK 25 and the Android command-line tools configured.

Refs meshtastic/design#128
Refs #6324

Summary by CodeRabbit

• New Features
  • Improved channel sharing with clearer Replace and Add options.
  • Add-mode share links now preserve channel settings without unnecessarily retuning radio configuration.
  • Replace-mode links continue to retain the complete channel configuration.
• Bug Fixes
  • Fixed shared channel URLs so they correctly reflect the selected sharing mode and preserve supported channel settings.

[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: a92159a6-d643-4580-88ec-80ab818948ee

📥 Commits

Reviewing files that changed from the base of the PR and between a3fe76f and 689945c.

📒 Files selected for processing (5)

• core/model/src/commonMain/kotlin/org/meshtastic/core/model/util/ChannelSet.kt
• core/model/src/commonTest/kotlin/org/meshtastic/core/model/util/ChannelSetUrlTest.kt
• feature/settings/src/commonMain/kotlin/org/meshtastic/feature/settings/radio/channel/ChannelScreen.kt
• feature/settings/src/commonMain/kotlin/org/meshtastic/feature/settings/radio/channel/ChannelShareState.kt
• feature/settings/src/commonTest/kotlin/org/meshtastic/feature/settings/radio/channel/ChannelScreenTest.kt

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📝 Walkthrough

Walkthrough

Channel sharing now omits lora_config from Add-mode URL payloads while preserving it for Replace mode. Share selection and URI generation move into ChannelShareState, with updated settings UI wiring and tests.

Changes

Channel sharing

Layer / File(s)	Summary
Channel URL payload contract core/model/src/commonMain/kotlin/.../ChannelSet.kt, core/model/src/commonTest/kotlin/.../ChannelSetUrlTest.kt	Add-mode encoding removes lora_config; Replace-mode encoding preserves it, with tests decoding and validating both payloads.
Share state and settings UI feature/settings/src/commonMain/kotlin/.../channel/*, feature/settings/src/commonTest/kotlin/.../channel/ChannelScreenTest.kt	ChannelShareState owns selection and URI generation, while ChannelScreen and ChannelShareDialog consume the computed URI; default Replace behavior is tested.

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

Possibly related issues

• meshtastic/Meshtastic-Android issue 6324 — Covers the same Replace/Add URL contract and lora_config handling.
• meshtastic/device-ui issue 350 — Addresses matching ChannelSet QR sharing semantics.
• meshtastic/web issue 1313 — Defines the shared Replace/Add URL behavior.
• meshtastic/Meshtastic-Apple issue 2126 — Covers omission of lora_config in Add URLs.
• meshtastic/design issue 128 — Describes the Replace/Add channel-sharing contract.

Possibly related PRs

• meshtastic/Meshtastic-Android#6320 — Adjusts related ChannelSet URL handling and test coverage for Add-mode encoding.

Suggested labels: bugfix

Suggested reviewers: jamesarich

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly matches the main change: updating the channel QR sharing contract and related behavior.
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.

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