refactor: extract workspace terminal sessions, improve sidebar drag-and-drop with nestable lists, and consolidate tab presentation logic

packages/app/src/terminal/runtime/terminal-output-session.ts

@@ -44,6 +44,10 @@ export type TerminalOutputSessionConsumeInput = {
   sequence: number;
 };
 
+export type TerminalOutputSessionReadSnapshotInput = {
+  terminalId: string | null;
+};
+
 export class TerminalOutputSession {
   private readonly listeners = new Set<() => void>();
   private readonly outputPump: TerminalOutputPump;
@@ -132,6 +136,10 @@ export class TerminalOutputSession {
     this.outputPump.append(input);
   }
 
+  readSnapshot(input: TerminalOutputSessionReadSnapshotInput): string {
+    return this.outputPump.readSnapshot(input);
+  }
+
   clearTerminal(input: { terminalId: string }): void {
     this.outputPump.clearTerminal(input);
     if (this.state.selectedTerminalId !== input.terminalId) {