feat(coding-agent): add resume scope toggle with async loading

- /resume and --resume now toggle between Current Folder and All sessions with Tab
- SessionManager.list() and listAll() are now async with optional progress callback
- Shows loading progress (e.g. Loading 5/42) while scanning sessions
- SessionInfo.cwd field shows session working directory in All view
- Lazy loading: All sessions only loaded when user presses Tab

closes #619

Co-authored-by: Thomas Mustier <mustierthomas@gmail.com>

packages/coding-agent/docs/sdk.md

@@ -636,12 +636,17 @@ const { session } = await createAgentSession({
   sessionManager: SessionManager.open("/path/to/session.jsonl"),
 });
 
-// List available sessions
-const sessions = SessionManager.list(process.cwd());
+// List available sessions (async with optional progress callback)
+const sessions = await SessionManager.list(process.cwd());
 for (const info of sessions) {
-  console.log(`${info.id}: ${info.firstMessage} (${info.messageCount} messages)`);
+  console.log(`${info.id}: ${info.firstMessage} (${info.messageCount} messages, cwd: ${info.cwd})`);
 }
 
+// List all sessions across all projects
+const allSessions = await SessionManager.listAll((loaded, total) => {
+  console.log(`Loading ${loaded}/${total}...`);
+});
+
 // Custom session directory (no cwd encoding)
 const customDir = "/path/to/my-sessions";
 const { session } = await createAgentSession({