feat(plugin): plugin marketplace, durable install persistence, skill manager

Add an in-app plugin marketplace fed by a remote web catalog: the host
plugin-inventory gateway gains marketplaceList/Install/Uninstall remotes,
a durable per-user install table reconciled against the actual profile, and
git/npm/tarball/bundle install paths with non-interactive git and vendored
pnpm. The Web Settings surface gains a sibling 插件市场 tab that lists the
catalog with recommended badges, repository links, and a combined sort
(recommended first, then catalog priority, then id).

Add a host + client skill manager: list local skills by direct filesystem
discovery, and install/uninstall/toggle/edit their SKILL.md from git/npm/
tarball/local sources in the writable user root.

Co-Authored-By: Claude <noreply@anthropic.com>

tsconfig.host.json

@@ -288,6 +288,7 @@
     { "path": "./packages/host/directory-picker-native" },
     { "path": "./packages/host/frontend-static" },
     { "path": "./packages/host/plugin-inventory" },
+    { "path": "./packages/host/skill-manager" },
     { "path": "./packages/host/webserver" },
     { "path": "./packages/sdk/client" },
     { "path": "./packages/sdk/protocol" },