feat(understand): auto-detect conversation language on first run

When /understand runs with no --language flag and no stored outputLanguage,
step 3.6 now infers the conversation language and — only when it is non-English
— confirms once before generating, then persists the choice to config.json.
English conversations keep the exact same silent `en` path; --language flag and
stored config still take priority. README documents the behavior; version
bumped 2.7.5 -> 2.7.6 across all five manifests (user-visible behavior change).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.cursor-plugin/plugin.json

@@ -2,7 +2,7 @@
   "name": "understand-anything",
   "displayName": "Understand Anything",
   "description": "AI-powered codebase understanding — analyze, visualize, and explain any project",
-  "version": "2.7.5",
+  "version": "2.7.6",
   "author": {
     "name": "Lum1104"
   },