feat: 现代化主题、日志配色与主界面布局

.codex/.gitignore

@@ -0,0 +1 @@
+config.toml

.trellis/spec/ui/theming.md

@@ -1,32 +1,99 @@
 # Theming & Accent Color
 
 Tailviewer's accent/theme color is user-configurable and updates the whole UI live
-(no restart). All accent colors derive from **one** base color (default `#0047AB`,
-`UISettings.DefaultThemeColor`).
+(no restart). All accent colors derive from **one** base color (default `#FF222280`,
+`UISettings.DefaultThemeColor`). The UI theme mode is persisted independently as
+`Light`, `Dark`, or `System`.
 
 ## Architecture
 
 ```
-UISettings.ThemeColor  ->  ThemeManager.Apply(Color)  ->  Application.Current.Resources
-                              |                                ["Primary", "PrimaryLight", ...]
-                              +--> TextBrushes.UpdateTheme     ["Secondary", "SecondaryLight", ...]
-                                   (mutable SolidColorBrush)           |
-                                                                       v
-                                                          XAML brushes bind via {DynamicResource}
+UISettings.ThemeColor + ThemeMode
+    -> ThemeManager.Apply(Color, ThemeMode)
+                                       |  ResolveDarkMode (System -> provider)
+                                       v
+                            ApplyCore(Color, bool) -> Application.Current.Resources
+                                       |                 ["Primary", "PrimaryLight", ...]
+                                       +--> TextBrushes.UpdateTheme/UpdateNeutral
+                                       +--> ThemeChanged
+                                              |              |
+                                              v              v
+                                   LogEntryListView rebuilds   settings ColorPickers
+                                   theme-aware TextBrushes
+                                                           |
+                                                           v
+                                              XAML brushes bind via {DynamicResource}
 ```
 
 - `src/Tailviewer/Ui/ThemePalette.cs` — pure helper `ThemePalette.Compute(Color)` derives
   the shade palette (light / lighter / dark / separator) by blending the base toward
   white/black. Pure & unit-testable (`ThemePaletteTest`).
-- `src/Tailviewer/Ui/ThemeManager.cs` — `Apply(Color)` writes the palette into
-  `Application.Current.Resources` under the well-known `Color` keys, then calls
-  `TextBrushes.UpdateTheme`. No-op when `Application.Current` is null (tests / design time).
+- `src/Tailviewer/Ui/ThemeManager.cs` — `Apply(Color, ThemeMode)` is the startup and
+  live-update entry point. `ThemeMode` controls the neutral UI (Light / Dark / System),
+  and the effective light/dark result selects the matching log-level defaults. All
+  callers publish the semantic resources, update the shared brushes, and raise
+  `ThemeChanged`.
+  Resource publication is a no-op when `Application.Current` is null (tests / design
+  time), but brush updates and the event still run.
 - `src/Tailviewer/Themes/Constants.xaml` — defines `SolidColorBrush` keys
   (`PrimaryBrush`, `SecondaryBrush`, …) whose `Color` is `{DynamicResource Primary}` etc.
   The `Color` keys themselves live **only** at application scope, set by `ThemeManager`.
 - `src/Tailviewer/Ui/LogView/TextBrushes.cs` — static brushes used by `FormattedText`
-  (line numbers, character code, selection). The three theme-derived brushes are mutable
-  `SolidColorBrush`es updated by `UpdateTheme(Color)`.
+  (line numbers, character code, selection). Every shared brush is frozen and
+  `UpdateTheme(Color)` / `UpdateNeutral(bool)` replace the references instead of
+  mutating a `SolidColorBrush`; this prevents WPF cross-thread ownership failures.
+  Each `TextBrushes` instance receives the active internal `LogLevelPalette` and owns
+  frozen level brushes. `LogEntryListView` rebuilds the instance and visible lines
+  after `ThemeChanged`.
+
+## Theme mode and system provider
+
+- `ThemeMode.Light` always resolves to light; `ThemeMode.Dark` always resolves to dark;
+  `ThemeMode.System` calls the injected `ISystemThemeProvider.IsDark()`.
+- `UISettings.Save` writes `thememode`. `Restore` accepts only defined enum values;
+  an invalid present value falls back to `Light`, while a missing `thememode` migrates
+  the legacy `darkmode` attribute (`true` -> `Dark`, otherwise `Light`).
+- `WindowsSystemThemeProvider` reads the Windows `AppsUseLightTheme` registry value,
+  marshals `UserPreferenceChanged` to `Application.Current.Dispatcher`, and is disposed
+  from `App.Exit`. Do not subscribe to `SystemEvents` from a static constructor.
+
+## Log-level default palette
+
+`LogLevelDefaults.Light` and `.Dark` are the single source for the seven level defaults.
+The exact pairs are:
+
+| Level | Light foreground / background | Dark foreground / background |
+|---|---|---|
+| TRACE | `#9AA5B1` / transparent | `#5B6472` / transparent |
+| DEBUG | `#6B7A8F` / transparent | `#7E8C9E` / transparent |
+| OTHER | `#7C6E9E` / transparent | `#8E7FAE` / transparent |
+| INFO | `#333333` / transparent | `#DCDCDC` / transparent |
+| WARNING | `#8A4D00` / `#FFF3D6` | `#F5D77E` / `#5A4700` |
+| ERROR | `#B3261E` / `#FDECEA` | `#FFB4AB` / `#6B1F1F` |
+| FATAL | `#FFFFFF` / `#C5221F` | `#FFFFFF` / `#9E1B1B` |
+
+`LogLevelSettings.IsCustom` is persisted as `iscustom`. Legacy level nodes without that
+attribute are custom when their stored pair differs from the new Light pair. A non-custom
+level gets frozen brushes from the active `LogLevelPalette`; a custom level owns frozen
+brushes from its stored colors. When a settings ColorPicker changes only one field for
+the first time, its ViewModel must seed the other stored field from the current effective
+palette default before setting `IsCustom=true`; otherwise a stale Light value can leak
+into the selected palette.
+
+### Theme-following log-level palette contract
+
+- The settings page exposes only the overall `ThemeMode` selector; there is no separate
+  log-level palette selector or persisted palette choice.
+- `ThemeManager.Apply(Color, ThemeMode)` resolves `System` through
+  `ISystemThemeProvider`, then sets `CurrentLogLevelPalette` to `Dark` for an effective
+  dark theme and `Light` otherwise.
+- Changing the overall theme updates an existing log viewer and log-level settings
+  through `ThemeChanged`, so default colors always follow the visible theme.
+- The settings reset action restores `UISettings.DefaultThemeColor`, calls
+  `ILogViewerSettings.RestoreDefaultColors()` to clear every `IsCustom` flag and restore
+  the Light persisted baseline, saves the settings, and reapplies the current
+  `ThemeMode` on the Dispatcher so both Light and Dark defaults become visible
+  immediately.
 
 ## Rules
 
@@ -82,13 +149,14 @@ those resource keys at app scope does **not** reach them. To re-theme an externa
 > **Warning: `{x:Static TextBrushes.Xxx}` freezes the brush.**
 >
 > WPF freezes a `Freezable` (SolidColorBrush) when it is assigned through a
-> `{x:Static}` reference on a dependency property. A frozen brush is read-only, so a
-> later `TextBrushes.UpdateTheme` that sets `.Color` throws
-> `InvalidOperationException` ("cannot set a property on a read-only object").
+> `{x:Static}` reference on a dependency property. A frozen brush must never be
+> mutated in place. All shared `TextBrushes` updates therefore create and assign a
+> new frozen brush, so a later theme change cannot read or write a brush owned by
+> another thread.
 >
 > - Theme-derived brushes that must change at runtime: bind in XAML via
->   `{DynamicResource PrimaryBrush}` (application-scope resource), OR keep them as
->   C#-only mutable brushes consumed by `FormattedText` (which does not freeze them).
+>   `{DynamicResource PrimaryBrush}` (application-scope resource), or replace the
+>   C# brush reference with a newly created frozen brush before redrawing.
 > - Never expose a theme-derived brush through `{x:Static}` in XAML.
 
 > **Warning: `DynamicResource` on a brush `Color` only works if the `Color` key is not
@@ -100,6 +168,13 @@ those resource keys at app scope does **not** reach them. To re-theme an externa
 - `Ui/ThemePaletteTest` — palette derivation (base == primary, fixed foregrounds,
   deterministic shades).
 - `Ui/TextBrushesTest` — defaults follow `UISettings.DefaultThemeColor`; `UpdateTheme`
-  recolors the three derived brushes.
-- `Settings/UISettingsTest` — `#0047AB` default, save/restore roundtrip, invalid-value
-  fallback, clone.
+  replaces frozen derived brushes; light/dark level palette selection creates the
+  expected frozen defaults and custom brushes remain unchanged.
+- `Settings/UISettingsTest` — `#FF222280` default, three-mode save/restore, legacy
+  `darkmode` migration, invalid-value fallback, clone.
+- `Settings/LogLevelDefaultsTest` and `Settings/LogViewerSettingsTest` — exact Light/Dark
+  pairs, legacy `iscustom` inference, and restoration of all default colors.
+- `Ui/Settings/LogLevelSettingsViewModelTest` — first custom edit seeds the unmodified
+  field from the active theme and calls `SaveAsync`.
+- `Ui/SettingsMainPanelViewModelTest` — the settings reset command restores the accent
+  color and theme-following log-level state.

.trellis/tasks/archive/2026-08/08-22-ui-semantic-layout/check.jsonl

@@ -0,0 +1,8 @@
+{"file": ".trellis/spec/ui/theming.md", "reason": "核对强调色 DynamicResource、冻结画刷、Metrolib 覆盖是否被破坏"}
+{"file": ".trellis/spec/ui/index.md", "reason": "UI 层整体规范与第三方依赖基线"}
+{"file": ".trellis/spec/ui/mvvm.md", "reason": "核对重排未引入 XAML 事件处理器或违反命令绑定约定"}
+{"file": ".trellis/spec/ui/project-structure.md", "reason": "核对未越界改动 BusinessLogic/ViewModel/本地化产物"}
+{"file": ".trellis/spec/build/index.md", "reason": "核对 warning-free 构建与项目格式约束"}
+{"file": ".trellis/spec/guides/code-reuse-thinking-guide.md", "reason": "核对硬编码色迁移完整性、无重复遗漏"}
+{"file": ".trellis/tasks/08-22-ui-semantic-layout/prd.md", "reason": "验收标准与红线清单，作为 check 的判定依据"}
+{"file": ".trellis/tasks/08-22-ui-semantic-layout/design.md", "reason": "边界、性能基线与回滚点，作为 check 的判定依据"}