[feat] Pin command palette actions to the sidebar

What problem are you trying to solve?

The home sidebar's nav is fixed: Workspaces, Automations, Tasks, Pull requests, and a few flag-gated entries. If the action I use all day isn't one of them, the only way to reach it is to open the command palette and search for it every time.

The one escape hatch today is a dedicated setting per action — #7191 added Show usage tab on sidebar for Usage (from #7096). That doesn't scale: each new "can I have X in the sidebar" request needs its own setting, migration, and CLI key.

Proposed solution

Let me pin any command palette action to the sidebar, directly from the palette:

• Every command row in the palette gets a pin toggle (shown on hover / on the highlighted row, reachable with Tab + Enter). Pinning doesn't run the command or close the palette.
• Pinned actions render under the built-in nav in the home sidebar, in both the expanded sidebar and the collapsed rail, with the command's own icon and title.
• Clicking a pinned action does exactly what selecting it in the palette does — including opening the palette on the sub-menu for commands like Toggle theme or Settings.
• Unpin from the palette (same toggle) or from the sidebar button's context menu.
• Pins are stored as command ids and resolved against the live palette, so nested commands (Settings → Appearance) work and an action that doesn't apply in the current context is hidden rather than shown dead.

I have a working implementation and will open a PR linked to this issue.

Workarounds you've tried

• The Show usage tab on sidebar setting — works, but only for Usage.
• Hotkeys — only a handful of commands have one, and they aren't discoverable the way a sidebar entry is.