Mercury Agent adds skill system, token saver

This looks like a meaningful platform step rather than a routine point release:

• –On-demand skill routing matters because it trims prompt bloat and avoids the bad UX of firing multiple weakly matched skills at once.
• –Token Saver Mode is a practical cost-control feature for autonomous agents, especially alongside the live usage display in the status bar.
• –Shipping standalone binaries removes setup friction for developers who want a local or self-hosted agent without depending on a Node install.
• –The shell permission fix is one of the highest-signal changes here because trust breaks fast if command guards are porous.