Preserve legacy style mode during migration

Constraint: legacy preferences may have defaultMode without activeStylePackId, and Raw style packs may still use the LLM path
Rejected: defaulting missing activeStylePackId to builtin.light | silently changes Raw, Structured, and Formal users during upgrade
Rejected: skipping script normalization for Raw LLM output | lets Simplified/Traditional preferences be bypassed by raw style packs
Confidence: high
Scope-risk: narrow
Directive: treat missing activeStylePackId as a migration case derived from defaultMode, not as the new-user default
Tested: cargo fmt --manifest-path src-tauri/Cargo.toml; git diff --check; cargo test --manifest-path src-tauri/Cargo.toml --lib types::tests::missing_active_style_pack_id_uses_legacy_default_mode; cargo test --manifest-path src-tauri/Cargo.toml --lib types::tests::explicit_active_style_pack_id_is_preserved; cargo test --manifest-path src-tauri/Cargo.toml --lib coordinator::dictation::tests::raw_llm_output_still_applies_script_preference; cargo test --manifest-path src-tauri/Cargo.toml --lib
Not-tested: full app build; desktop runtime smoke on macOS/Windows

openless-all/app/src-tauri/src/coordinator/dictation.rs

@@ -289,7 +289,7 @@ async fn run_streaming_polish(
 fn finalize_polished_text(
     polished: String,
     translation_active: bool,
-    raw_uses_llm: bool,
+    _raw_uses_llm: bool,
     mode: PolishMode,
     polish_error: &Option<String>,
     chinese_script_preference: crate::types::ChineseScriptPreference,
@@ -302,7 +302,7 @@ fn finalize_polished_text(
     let should_force_script = if translation_active {
         polish_error.is_some()
     } else {
-        (!raw_uses_llm && mode == PolishMode::Raw) || polish_error.is_some()
+        mode == PolishMode::Raw || polish_error.is_some()
     };
     let polished = if should_force_script {
         apply_chinese_script_preference(&polished, chinese_script_preference)
@@ -1650,6 +1650,22 @@ mod tests {
         assert_eq!(result, "Open AI");
     }
 
+    #[test]
+    fn raw_llm_output_still_applies_script_preference() {
+        let result = finalize_polished_text(
+            "繁體".into(),
+            false,
+            true,
+            PolishMode::Raw,
+            &None,
+            ChineseScriptPreference::Simplified,
+            &[],
+            false,
+        );
+
+        assert_eq!(result, "繁体");
+    }
+
     #[test]
     fn non_streamed_output_still_applies_correction_rules() {
         let rules = vec![correction_rule("Open AI", "OpenAI")];

openless-all/app/src-tauri/src/types.rs

@@ -644,8 +644,8 @@ struct UserPreferencesWire {
     dictation_hotkey: Option<ShortcutBinding>,
     default_mode: PolishMode,
     enabled_modes: Vec<PolishMode>,
-    #[serde(default = "default_active_style_pack_id")]
-    active_style_pack_id: String,
+    #[serde(default)]
+    active_style_pack_id: Option<String>,
     #[serde(default)]
     style_system_prompts: StyleSystemPrompts,
     #[serde(default)]
@@ -711,7 +711,7 @@ impl Default for UserPreferencesWire {
             dictation_hotkey: None,
             default_mode: prefs.default_mode,
             enabled_modes: prefs.enabled_modes,
-            active_style_pack_id: prefs.active_style_pack_id,
+            active_style_pack_id: Some(prefs.active_style_pack_id),
             style_system_prompts: prefs.style_system_prompts,
             custom_style_prompts: prefs.custom_style_prompts,
             launch_at_login: prefs.launch_at_login,
@@ -767,11 +767,10 @@ impl<'de> Deserialize<'de> for UserPreferences {
             dictation_hotkey,
             default_mode: wire.default_mode,
             enabled_modes: wire.enabled_modes,
-            active_style_pack_id: if wire.active_style_pack_id.trim().is_empty() {
-                builtin_style_pack_id(wire.default_mode).to_string()
-            } else {
-                wire.active_style_pack_id
-            },
+            active_style_pack_id: wire
+                .active_style_pack_id
+                .filter(|id| !id.trim().is_empty())
+                .unwrap_or_else(|| builtin_style_pack_id(wire.default_mode).to_string()),
             style_system_prompts: wire
                 .style_system_prompts
                 .with_legacy_custom_prompts(&wire.custom_style_prompts),
@@ -1770,6 +1769,33 @@ mod tests {
         assert!(prefs.custom_style_prompts.has_for_mode(PolishMode::Formal));
     }
 
+    #[test]
+    fn missing_active_style_pack_id_uses_legacy_default_mode() {
+        let prefs: UserPreferences = serde_json::from_str(
+            r#"{
+                "defaultMode": "structured"
+            }"#,
+        )
+        .unwrap();
+
+        assert_eq!(prefs.default_mode, PolishMode::Structured);
+        assert_eq!(prefs.active_style_pack_id, BUILTIN_STYLE_PACK_STRUCTURED_ID);
+    }
+
+    #[test]
+    fn explicit_active_style_pack_id_is_preserved() {
+        let prefs: UserPreferences = serde_json::from_str(
+            r#"{
+                "defaultMode": "formal",
+                "activeStylePackId": "custom.meeting"
+            }"#,
+        )
+        .unwrap();
+
+        assert_eq!(prefs.default_mode, PolishMode::Formal);
+        assert_eq!(prefs.active_style_pack_id, "custom.meeting");
+    }
+
     #[test]
     fn legacy_custom_style_prompts_are_not_appended_twice() {
         let base = StyleSystemPrompts::default();