[Feature] Select sidebar chats directly with Cmd+1 … Cmd+9 (numbered quick switch)

Pre-submission checklist

• I searched existing issues and confirmed this isn't a duplicate (related: #725, which asks for a keybindings editor — this is a concrete shortcut request of its own)
• I've read CONTRIBUTING.md

Category

UI / 界面体验 · UI / UX

Agent framework

ZCode Agent（自研） — the task/chat list in the desktop app's left sidebar.

Use case · 使用场景

I run many chats/tasks in parallel and the sidebar is my main navigation surface. Right now there is no way to jump directly to a specific chat:

• Mouse only: scroll the sidebar and click the chat
• Cmd+[ / Cmd+] go back/forward through task history, and Shift+Cmd+[ / Shift+Cmd+] switch to the previous/next conversation — both are sequential, so reaching a specific chat among 8+ open ones takes multiple keystrokes or a mouse trip

Like browser tabs, chat position in the sidebar is stable during a work session, so direct numbered access would map naturally to it.

Proposal · 建议方案

Add Cmd+1 … Cmd+9 to select the 1st–9th chat/task in the sidebar directly (and optionally Cmd+9 = last, or Cmd+0 = 10th). Details that would make it great:

• Match the sidebar's visible top-to-bottom order within the current Group/Project filter, so the mapping is predictable
• Show the number as a subtle badge on each sidebar row (always, or while holding a modifier / on hover) for discoverability
• If #725's keybindings editor lands, keep these rebindable

Expected value · 预期价值

• One keystroke to any open chat instead of sequential stepping or mouse clicks
• Consistent with numbered-tab conventions users already know from browsers, Slack, and VS Code
• Directly supports ZCode's core strength — running multiple agents in parallel — by making the sidebar keyboard-navigable

Your perceived priority

中 · Medium

ZCode version / environment

ZCode Desktop 3.9.2 (3.9.2.6069) · macOS 15.6 (24G84), Apple Silicon

Additional context

• Current shortcuts per the official docs (https://zcode.z.ai/en/docs/keyboard-shortcuts): Cmd+N new task, Cmd+[ / Cmd+] previous/next task or workspace, Shift+Cmd+[ / Shift+Cmd+] previous/next conversation — no direct numbered selection exists
• Related: #725 (terminal maximize shortcut + keybindings editor proposal)

The issue names no implementation files, tests, or entry points; start by locating the desktop app's existing Cmd+[ and Cmd+] shortcut handling and sidebar task ordering. Done means Cmd+1 through Cmd+9 select chats in the visible Group/Project order, with behavior for unavailable chats and optional badges or rebinding clarified.