feat(electrobun): file management — CodeMirror editor, PDF viewer, CSV table, real file I/O

- CodeEditor: CodeMirror 6 with Catppuccin theme, 15+ languages, Ctrl+S save,
  dirty tracking, save-on-blur
- PdfViewer: pdfjs-dist canvas rendering, zoom 0.5-3x, HiDPI, lazy page load
- CsvTable: RFC 4180 parser, delimiter auto-detect, sortable columns, sticky header
- FileBrowser: real filesystem via files.list/read/write RPC, lazy dir loading,
  file type routing (code→editor, pdf→viewer, csv→table, images→display)
- 10MB size gate, binary detection, base64 encoding for non-text files

ui-electrobun/src/mainview/agent-store.svelte.ts

@@ -74,6 +74,54 @@ let sessions = $state<Record<string, AgentSession>>({});
 // Grace period timers for cleanup after done/error
 const cleanupTimers = new Map<string, ReturnType<typeof setTimeout>>();
 
+// Debounce timer for message persistence
+const msgPersistTimers = new Map<string, ReturnType<typeof setTimeout>>();
+
+// ── Session persistence helpers ─────────────────────────────────────────────
+
+function persistSession(session: AgentSession): void {
+  appRpc.request['session.save']({
+    projectId: session.projectId,
+    sessionId: session.sessionId,
+    provider: session.provider,
+    status: session.status,
+    costUsd: session.costUsd,
+    inputTokens: session.inputTokens,
+    outputTokens: session.outputTokens,
+    model: session.model,
+    error: session.error,
+    createdAt: session.messages[0]?.timestamp ?? Date.now(),
+    updatedAt: Date.now(),
+  }).catch((err: unknown) => {
+    console.error('[session.save] persist error:', err);
+  });
+}
+
+function persistMessages(session: AgentSession): void {
+  // Debounce: batch message saves every 2 seconds
+  const existing = msgPersistTimers.get(session.sessionId);
+  if (existing) clearTimeout(existing);
+
+  const timer = setTimeout(() => {
+    msgPersistTimers.delete(session.sessionId);
+    const msgs = session.messages.map((m) => ({
+      sessionId: session.sessionId,
+      msgId: m.id,
+      role: m.role,
+      content: m.content,
+      toolName: m.toolName,
+      toolInput: m.toolInput,
+      timestamp: m.timestamp,
+    }));
+    if (msgs.length === 0) return;
+    appRpc.request['session.messages.save']({ messages: msgs }).catch((err: unknown) => {
+      console.error('[session.messages.save] persist error:', err);
+    });
+  }, 2000);
+
+  msgPersistTimers.set(session.sessionId, timer);
+}
+
 // ── RPC event listeners (registered once) ────────────────────────────────────
 
 let listenersRegistered = false;
@@ -104,6 +152,7 @@ function ensureListeners() {
 
     if (converted.length > 0) {
       session.messages = [...session.messages, ...converted];
+      persistMessages(session);
     }
   });
 
@@ -119,8 +168,18 @@ function ensureListeners() {
     session.status = normalizeStatus(payload.status);
     if (payload.error) session.error = payload.error;
 
+    // Persist on every status change
+    persistSession(session);
+
     // Schedule cleanup after done/error (Fix #2)
     if (session.status === 'done' || session.status === 'error') {
+      // Flush any pending message persistence immediately
+      const pendingTimer = msgPersistTimers.get(session.sessionId);
+      if (pendingTimer) {
+        clearTimeout(pendingTimer);
+        msgPersistTimers.delete(session.sessionId);
+      }
+      persistMessages(session);
       scheduleCleanup(session.sessionId, session.projectId);
     }
   });
@@ -427,5 +486,57 @@ export function clearSession(projectId: string): void {
   }
 }
 
+/**
+ * Load the last session for a project from SQLite (for restart recovery).
+ * Restores session state + messages into the reactive store.
+ * Only restores done/error sessions (running sessions are gone after restart).
+ */
+export async function loadLastSession(projectId: string): Promise<boolean> {
+  ensureListeners();
+  try {
+    const { session } = await appRpc.request['session.load']({ projectId });
+    if (!session) return false;
+
+    // Only restore completed sessions (running sessions can't be resumed)
+    if (session.status !== 'done' && session.status !== 'error') return false;
+
+    // Load messages for this session
+    const { messages: storedMsgs } = await appRpc.request['session.messages.load']({
+      sessionId: session.sessionId,
+    });
+
+    const restoredMessages: AgentMessage[] = storedMsgs.map((m: {
+      msgId: string; role: string; content: string;
+      toolName?: string; toolInput?: string; timestamp: number;
+    }) => ({
+      id: m.msgId,
+      role: m.role as MsgRole,
+      content: m.content,
+      toolName: m.toolName,
+      toolInput: m.toolInput,
+      timestamp: m.timestamp,
+    }));
+
+    sessions[session.sessionId] = {
+      sessionId: session.sessionId,
+      projectId: session.projectId,
+      provider: session.provider,
+      status: normalizeStatus(session.status),
+      messages: restoredMessages,
+      costUsd: session.costUsd,
+      inputTokens: session.inputTokens,
+      outputTokens: session.outputTokens,
+      model: session.model,
+      error: session.error,
+    };
+
+    projectSessionMap.set(projectId, session.sessionId);
+    return true;
+  } catch (err) {
+    console.error('[loadLastSession] error:', err);
+    return false;
+  }
+}
+
 /** Initialize listeners on module load. */
 ensureListeners();