Add a setting to disable the Work Board / 'Yesterday's sessions' panel auto-opening on startup

What happened

On the macOS desktop app, after a reboot / fresh login, a Work Board panel titled "Yesterday's sessions" / "Yesterday's work" auto-opens in the preview pane on startup. It shows recent session threads for the last repo with Open PR / Branch / Diff affordances.

There is currently no way to prevent this from opening automatically:

• No documented settings.json key (workBoard, preview, layout, etc.).
• Not driven by any user hook, scheduled task, or cron (verified locally).
• Closing the panel does not reliably stop it from being restored on the next launch.

Request

A user-configurable toggle to disable the Work Board auto-open on startup — e.g. a settings.json key such as:

{ "workBoard": { "autoOpenOnStartup": false } }

This is the same class of request as the preview-pane auto-open toggle in #51587 — a way to opt out of a panel opening itself. Some users start each session by returning to specific work and would prefer a clean pane on launch.

Environment

• Claude Code desktop app, macOS.