chore: rename npm scope from @valknar to @valknarthing

Updated package names across the project:
- @valknar/llmx → @valknarthing/llmx
- @valknar/llmx-sdk → @valknarthing/llmx-sdk
- @valknar/llmx-responses-api-proxy → @valknarthing/llmx-responses-api-proxy

Also updated:
- GitHub repository URLs (valknar → valknarthing)
- GitHub Actions workflow scope configuration
- README installation instructions

llmx-cli/package.json

@@ -1,5 +1,5 @@
 {
-  "name": "@valknar/llmx",
+  "name": "@valknarthing/llmx",
   "version": "0.1.0",
   "license": "Apache-2.0",
   "description": "LLMX CLI - Multi-provider coding agent powered by LiteLLM",
@@ -16,7 +16,7 @@
   ],
   "repository": {
     "type": "git",
-    "url": "git+https://github.com/valknar/llmx.git",
+    "url": "git+https://github.com/valknarthing/llmx.git",
     "directory": "llmx-cli"
   }
 }