refactor(web): dashboard typography & contrast pass

Removes the global `uppercase` + `font-mondwest` from the App.tsx root
that forced every page to opt-out, replaces stacked-alpha text colors
with semantic tokens for WCAG-AA contrast across all 7 themes, and
applies the new `text-display` utility from @nous-research/ui@0.16.0
on intentional brand chrome (page titles, sidebar headings, segmented
filters) only. Bumps every sub-12px arbitrary text size to text-xs.

Also widens the dashboard plugin routes (/api/dashboard/agent-plugins/
{name:path}/...) so category-namespaced plugins like observability/
langfuse and image_gen/openai can be enable/disabled from the dashboard
— previously the FE encodeURIComponent-ed the slash and the backend
{name} route rejected it. _validate_plugin_name still blocks .. and
backslash, and strips leading/trailing slash.

Touches sessions/env/keys page chrome and adds two new i18n keys
(`overview`, `showMore`/`showLess`) across all 18 locales.

Squashes 19 commits from PR #28832.

Co-authored-by: Hermes <noreply@nousresearch.com>

web/src/lib/api.ts

@@ -51,6 +51,11 @@ export async function fetchJSON<T>(url: string, init?: RequestInit): Promise<T>
   return res.json();
 }
 
+/** Encode a plugin registry key for URL paths (preserves `/` segment separators). */
+function pluginPath(name: string): string {
+  return name.split("/").map(encodeURIComponent).join("/");
+}
+
 async function getSessionToken(): Promise<string> {
   if (_sessionToken) return _sessionToken;
   const injected = window.__HERMES_SESSION_TOKEN__;
@@ -293,25 +298,25 @@ export const api = {
 
   enableAgentPlugin: (name: string) =>
     fetchJSON<{ ok: boolean; name: string; unchanged?: boolean }>(
-      `/api/dashboard/agent-plugins/${encodeURIComponent(name)}/enable`,
+      `/api/dashboard/agent-plugins/${pluginPath(name)}/enable`,
       { method: "POST" },
     ),
 
   disableAgentPlugin: (name: string) =>
     fetchJSON<{ ok: boolean; name: string; unchanged?: boolean }>(
-      `/api/dashboard/agent-plugins/${encodeURIComponent(name)}/disable`,
+      `/api/dashboard/agent-plugins/${pluginPath(name)}/disable`,
       { method: "POST" },
     ),
 
   updateAgentPlugin: (name: string) =>
     fetchJSON<AgentPluginUpdateResponse>(
-      `/api/dashboard/agent-plugins/${encodeURIComponent(name)}/update`,
+      `/api/dashboard/agent-plugins/${pluginPath(name)}/update`,
       { method: "POST" },
     ),
 
   removeAgentPlugin: (name: string) =>
     fetchJSON<{ ok: boolean; name: string }>(
-      `/api/dashboard/agent-plugins/${encodeURIComponent(name)}`,
+      `/api/dashboard/agent-plugins/${pluginPath(name)}`,
       { method: "DELETE" },
     ),
 
@@ -324,7 +329,7 @@ export const api = {
 
   setPluginVisibility: (name: string, hidden: boolean) =>
     fetchJSON<{ ok: boolean; name: string; hidden: boolean }>(
-      `/api/dashboard/plugins/${encodeURIComponent(name)}/visibility`,
+      `/api/dashboard/plugins/${pluginPath(name)}/visibility`,
       {
         method: "POST",
         headers: { "Content-Type": "application/json" },