feat: add per-chat queues and richer queue controls

[vyacheslav666-cpu]

What changed

• added safe queue item editing, retry actions, and drag-and-drop reordering;
• added independent queues and leases for each ChatGPT conversation;
• migrated queue storage to v4 with per-scope revisions and tombstones;
• preserved concurrent writes made by different chats;
• improved keyboard input, clear confirmation, accessibility labels, and persisted panel collapse state;
• added unit regressions and local browser E2E scenarios;
• rebuilt the installable userscript and updated documentation.

Why

Real Chrome and Tampermonkey E2E testing exposed a localStorage read-modify-write race: simultaneous updates from different chat queues could overwrite the shared document and silently lose a prompt. Per-chat revisions now allow a stale writer to restore a newer scope instead of deleting it.

User impact

Users can safely run independent queues in multiple chats, edit and reorder pending prompts, retry failed items, and use improved keyboard and panel controls without mixing or losing queue entries.

Validation

• npm run validate
• Vitest: 41/41 passed
• local browser E2E for per-chat queues and panel actions
• real Chrome + Tampermonkey test with simultaneous generation in two chats

The unrelated research document is intentionally excluded.