fix(refresh-marketplace): pass --scope project to claude plugin update

Without `--scope project`, `claude plugin update <name>@agnes` operated
at user scope (the default) instead of updating the project-scoped
install — so version bumps in the served manifest never propagated to
the workspace, even though `claude plugin install` correctly used
`--scope project` for the missing-plugin path.

Mirrors the install line in the same function. Any change refresh-
marketplace makes to a plugin must now stay in project scope —
consistent with the SessionStart hook firing per-workspace.

cli/commands/refresh_marketplace.py

@@ -361,7 +361,7 @@ def _reconcile_with_manifest(
     for name in to_update:
         target = f"{name}@{MARKETPLACE_NAME}"
         result = subprocess.run(
-            ["claude", "plugin", "update", target],
+            ["claude", "plugin", "update", target, "--scope", "project"],
             capture_output=True, text=True, encoding="utf-8", errors="replace", check=False,
         )
         if result.returncode != 0: