File-based project save/load, AI chat formatting, text edit fix

Project files (.vtn):
- Save Project: serializes transcript, speakers, audio path to JSON file
- Open Project: loads .vtn file, restores audio/transcript/speakers
- User chooses filename and location via save dialog
- Replaces SQLite-based project persistence (DB commands remain for future use)
- Text edits update in-memory store immediately, persist on explicit save
- Fix Windows path separator in project name extraction

AI chat:
- Markdown rendering in assistant messages (headers, lists, bold, code)
- Better visual distinction with border-left accents
- Styled markdown elements for dark theme

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src-tauri/src/commands/project.rs

@@ -1,10 +1,48 @@
 use serde::{Deserialize, Serialize};
+use std::fs;
 use tauri::State;
 
 use crate::db::models::Project;
 use crate::db::queries;
 use crate::state::AppState;
 
+// ── File-based project types ────────────────────────────────────
+
+#[derive(Serialize, Deserialize)]
+pub struct ProjectFile {
+    pub version: u32,
+    pub name: String,
+    pub audio_file: String,
+    pub created_at: String,
+    pub segments: Vec<ProjectFileSegment>,
+    pub speakers: Vec<ProjectFileSpeaker>,
+}
+
+#[derive(Serialize, Deserialize)]
+pub struct ProjectFileSegment {
+    pub text: String,
+    pub start_ms: i64,
+    pub end_ms: i64,
+    pub speaker: Option<String>,
+    pub is_edited: bool,
+    pub words: Vec<ProjectFileWord>,
+}
+
+#[derive(Serialize, Deserialize)]
+pub struct ProjectFileWord {
+    pub word: String,
+    pub start_ms: i64,
+    pub end_ms: i64,
+    pub confidence: f64,
+}
+
+#[derive(Serialize, Deserialize)]
+pub struct ProjectFileSpeaker {
+    pub label: String,
+    pub display_name: Option<String>,
+    pub color: String,
+}
+
 // ── Input types for save_project_transcript ──────────────────────
 
 #[derive(Deserialize)]
@@ -243,3 +281,17 @@ pub fn load_project_transcript(
         speakers: speaker_outputs,
     }))
 }
+
+// ── File-based project commands ─────────────────────────────────
+
+#[tauri::command]
+pub fn save_project_file(path: String, project: ProjectFile) -> Result<(), String> {
+    let json = serde_json::to_string_pretty(&project).map_err(|e| e.to_string())?;
+    fs::write(&path, json).map_err(|e| format!("Failed to save project: {e}"))
+}
+
+#[tauri::command]
+pub fn load_project_file(path: String) -> Result<ProjectFile, String> {
+    let json = fs::read_to_string(&path).map_err(|e| format!("Failed to read project: {e}"))?;
+    serde_json::from_str(&json).map_err(|e| format!("Failed to parse project: {e}"))
+}

src-tauri/src/lib.rs

@@ -10,8 +10,8 @@ use tauri::Manager;
 use commands::ai::{ai_chat, ai_configure, ai_list_providers};
 use commands::export::export_transcript;
 use commands::project::{
-    create_project, delete_project, get_project, list_projects, load_project_transcript,
-    save_project_transcript, update_segment,
+    create_project, delete_project, get_project, list_projects, load_project_file,
+    load_project_transcript, save_project_file, save_project_transcript, update_segment,
 };
 use commands::settings::{load_settings, save_settings};
 use commands::system::{get_data_dir, llama_list_models, llama_start, llama_status, llama_stop};
@@ -41,6 +41,8 @@ pub fn run() {
             save_project_transcript,
             load_project_transcript,
             update_segment,
+            save_project_file,
+            load_project_file,
             transcribe_file,
             run_pipeline,
             download_diarize_model,