Fix stale settings saves resetting style selection

[snvtac]

User description

Summary

• Preserve style-pack-owned preference fields when generic settings saves persist a full preferences payload.
• Add a locked PreferencesStore write path so a stale settings payload cannot roll back the current active style pack.
• Emit the actual saved preferences after set_settings and set_update_channel persist.

Root Cause

Generic settings saves send a complete UserPreferences snapshot. If the user switches to a local style pack and a later settings save uses an older snapshot, that stale payload can overwrite active_style_pack_id and related legacy style fields, sending the app back to the previous formal/builtin style.

Fix

The generic settings save path now treats style-pack preferences as owned by the style-pack commands. Before writing a generic settings payload, PreferencesStore::set_preserving_current_style_preferences copies the current store style fields under the same store lock used for the disk write and in-memory update. Style-pack commands still use the normal store write path, so intentional style changes continue to persist.

Fixes #742.

Validation

• rustfmt --edition 2021 --check openless-all/app/src-tauri/src/commands/settings.rs openless-all/app/src-tauri/src/persistence/preferences.rs openless-all/app/src-tauri/src/types.rs
• cargo test settings
• cargo test sync_style_pack_preferences
• cargo test set_preserving_current_style_preferences
• git diff --check

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PR Type

Bug fix

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Description

• Preserve active style pack across generic settings saves

• Add new write path that copies current style fields before persisting

• Add tests verifying style preferences are retained

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Diagram Walkthrough

flowchart LR
  A["Generic settings save"] --> B["read_settings()"]
  B --> C["preserve_style_preferences_from(current)"]
  C --> D["atomic_write to disk"]
  D --> E["Style fields unchanged"]

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File Walkthrough

	Relevant files
Bug fix	settings.rs Preserve style in settings persist path                                    openless-all/app/src-tauri/src/commands/settings.rs Added write_settings_preserving_current_style_preferences trait method Updated persist_settings and set_settings to use the new preserving write path Added unit tests simulating race conditions and stale payloads Emit actual saved preferences after write +141/-10
Enhancement	preferences.rs Add preserving write to PreferencesStore                                  openless-all/app/src-tauri/src/persistence/preferences.rs Added set_preserving_current_style_preferences method Copies style fields from current store state before writing Added test verifying disk and in-memory consistency +53/-1    types.rs Add style preservation helper                                                        openless-all/app/src-tauri/src/types.rs Added preserve_style_preferences_from method on UserPreferences Copies default_mode, enabled_modes, active_style_pack_id, style_system_prompts, custom_style_prompts +10/-0

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[github-actions]

PR Reviewer Guide 🔍

Here are some key observations to aid the review process:

🎫 Ticket compliance analysis 🔶 742 - Partially compliant Compliant requirements: 选择任意本地风格包后，应用重启或等待一段时间后仍保持该选择。 后续转写/润色使用用户最后一次激活的风格包，而不是自动回退到“正式表达”。 Non-compliant requirements: 若保存失败或配置被重置，界面能给出可观察的错误/提示，便于定位。 Requires further human verification: The third requirement (UI error feedback on save failure) is not implemented in this PR; the error is only propagated as a string result. It may be addressed in a separate UI change or considered out of scope.

⏱️ Estimated effort to review: 2 🔵🔵⚪⚪⚪

🧪 PR contains tests

🔒 No security concerns identified

⚡ No major issues detected