docs(plugin-system): reference for install, injection, and required/optional split

Adds a bilingual reference explaining how plugins are installed and composed
(bundles, patches, profiles, the Loader), how they are injected and activated
(Cordis inject/provide, fiber PENDING), and a dependency-derived split of the
shipped base bundle into system-required and freely optional plugins. Links the
plugin-inventory README to it and excludes the desktop build output from the
translation-pairing corpus scan.

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

scripts/translation-pairing.ts

@@ -159,6 +159,8 @@ export const TRANSLATION_SCOPE_GLOB_EXCLUDES = [
   '**/__pycache__/**',
   '**/.pytest_cache/**',
   'apps/web/dist/**',
+  'apps/desktop/dist/**',
+  'apps/desktop/build/harness/**',
   '.artifacts/**',
   'python/sdk-runtime/src/deepseek_harness_runtime/runtime/dsh-jsonrpc-agent-*/**',
   'python/sdk-runtime/src/deepseek_harness_runtime/runtime/node/**',