feat: expand character editor to show all v2/v3 character card fields

Added support for all v2/v3 character card fields in the character editor UI:
- Description (10-row textarea)
- Scenario
- Message Example
- Post-History Instructions
- Alternate Greetings (one per line)
- Tags (comma-separated)
- Creator
- Character Version
- Creator Notes

Updated frontend to load and save all fields, and backend update_character
command to accept all new parameters. This allows imported v3 character cards
to display their full details, especially the description field which contains
the main character information.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src-tauri/src/lib.rs

@@ -630,6 +630,15 @@ fn update_character(
     system_prompt: String,
     greeting: Option<String>,
     personality: Option<String>,
+    description: Option<String>,
+    scenario: Option<String>,
+    mes_example: Option<String>,
+    post_history: Option<String>,
+    alt_greetings: Option<Vec<String>>,
+    tags: Option<Vec<String>>,
+    creator: Option<String>,
+    character_version: Option<String>,
+    creator_notes: Option<String>,
     avatar_path: Option<String>,
 ) -> Result<(), String> {
     let mut character = get_active_character();
@@ -637,6 +646,15 @@ fn update_character(
     character.system_prompt = system_prompt;
     character.greeting = greeting;
     character.personality = personality;
+    character.description = description;
+    character.scenario = scenario;
+    character.mes_example = mes_example;
+    character.post_history_instructions = post_history;
+    character.alternate_greetings = alt_greetings.unwrap_or_default();
+    character.tags = tags.unwrap_or_default();
+    character.creator = creator;
+    character.character_version = character_version;
+    character.creator_notes = creator_notes;
     character.avatar_path = avatar_path;
     save_character(&character)
 }