Hidden --resolve-only flag reports which marketplace --from-link would reuse

What

A marketplace is a catalogue of plugins that Claude Code can install from. The command that adds one has a new hidden flag, --resolve-only.

• It must be used with --from-link. Without it, the command stops with "--resolve-only needs --from-link".
• It adds nothing. It prints one line of JSON, {"existing": ...}, naming the already-added marketplace that --from-link would reuse.
• It cannot be combined with --sparse or --scope.
• --from-link now checks for an existing marketplace for any source. Before, it did so only for certain kinds of source.

Why

A program handling an install link can ask whether a marketplace is already added without changing anything. Because --from-link now looks for an existing marketplace for every source, it is more likely to reuse one you already have instead of adding a duplicate.