feat(dashboard): add Plugins page with enable/disable, auth status, install/remove

- New PluginsPage.tsx: full plugin management UI (list, enable/disable,
  install from git, remove, git pull updates, provider picker)
- Backend: dashboard_set_agent_plugin_enabled now also toggles the
  plugin's toolset in platform_toolsets so enabling actually makes
  tools visible in agent sessions
- Backend: /api/dashboard/plugins/hub returns auth_required + auth_command
  per plugin (checks tool registry check_fn)
- Frontend: auth_required shown as Badge + CommandBlock with copy-able
  auth command
- Fix: Select overflow in providers card (min-w-0 grid cells, removed
  truncate/overflow-hidden that clipped dropdown)
- Refactor: _install_plugin_core extracted for non-interactive reuse,
  PluginOperationError for structured error handling
- i18n: en/zh/types updated with all new plugin page strings

web/src/i18n/en.ts

@@ -76,6 +76,7 @@ export const en: Translations = {
       logs: "Logs",
       models: "Models",
       profiles: "profiles : multi agents",
+      plugins: "Plugins",
       sessions: "Sessions",
       skills: "Skills",
     },
@@ -84,6 +85,7 @@ export const en: Translations = {
     navigation: "Navigation",
     openDocumentation: "Open documentation in a new tab",
     openNavigation: "Open navigation",
+    pluginNavSection: "Plugins",
     sessionsActiveCount: "{count} active",
     statusOverview: "Status overview",
     system: "System",
@@ -256,6 +258,45 @@ export const en: Translations = {
     renamed: "Renamed",
   },
 
+  pluginsPage: {
+    contextEngineLabel: "Context engine",
+    dashboardSlots: "Dashboard slots",
+    disableRuntime: "Disable",
+    enableAfterInstall: "Enable after install",
+    enableRuntime: "Enable",
+    forceReinstall: "Force reinstall (delete existing folder first)",
+    headline:
+      "Discover, install, enable, and update Hermes plugins (`hermes plugins` parity).",
+    identifierLabel: "Git URL or owner/repo",
+    inactive: "inactive",
+    installBtn: "Install from Git",
+    installHeading: "Install from GitHub / Git URL",
+    installHint: "Use owner/repo shorthand or a full https:// or git@ clone URL.",
+    memoryProviderLabel: "Memory provider",
+    missingEnvWarn: "Set these in Keys before the plugin can run:",
+    noDashboardTab: "No dashboard tab",
+    openTab: "Open",
+    orphanHeading: "Dashboard-only extensions (no agent plugin.yaml match)",
+    pluginListHeading: "Installed plugins",
+    providerDefaults: "built-in / default",
+    providersHeading: "Runtime provider plugins",
+    providersHint:
+      "Writes memory.provider (empty = built-in) and context.engine to config.yaml. Takes effect next session.",
+    refreshDashboard: "Rescan dashboard extensions",
+    removeConfirm: "Remove this plugin from ~/.hermes/plugins/?",
+    removeHint: "Only user-installed plugins under ~/.hermes/plugins can be removed.",
+    rescanHeading: "SPA plugin registry",
+    rescanHint: "Rescan after adding files on disk so the dashboard sidebar picks up new manifests.",
+    runtimeHeading: "Gateway runtime (YAML plugins)",
+    saveProviders: "Save provider settings",
+    savedProviders: "Provider settings saved.",
+    sourceBadge: "Source",
+    authRequired: "Auth required",
+    authRequiredHint: "Run this command to authenticate:",
+    updateGit: "Git pull",
+    versionBadge: "Version",
+  },
+
   skills: {
     title: "Skills",
     searchPlaceholder: "Search skills and toolsets...",