Plugin install gains replace options and new failure reasons, mostly inactive

What

Plugins are add-ons that extend Claude Code, installed from marketplaces (catalogs of plugins). The routine that installs them has new parts:

• New options: replaceInstalledCopy, replaceOnlyPluginIds, carrySettingsFrom, and surface, which defaults to "cli". A result can also carry a switched field.
• New failure reasons: "installed-from-other-marketplace", "more-installed-than-shown", "plugin-directory-unavailable" (a dependency's directory is unavailable) and "directory-pin-unsatisfied". Each currently shows the generic Failed to install plugin message with failureCode "dependency_resolution_failed".
• Each dependency's entry is now checked for a policy block. The marketplace policy check moved into a helper.
• Policy-block messages are now built by a shared message builder. Before, they were fixed text such as "is blocked by your organization's policy and cannot be installed", from the reasons "blocked-by-policy" and "marketplace-blocked-by-policy".
• Several pieces are stubbed out in this build: the list of installed copies is hardcoded empty ([Pe, ...Le] = []), copiesInOtherProjects is [], some blocks are if (!1), and some message endings are empty. As a result the replace and other-marketplace paths cannot fire yet.

Why

Most of this cannot take effect yet. In practice, a plugin install that hits one of the new reasons fails with a generic message, and policy-block wording comes from a shared builder. The inactive parts deal with plugins already installed from a different marketplace.