Strix LLM Documentation and Config Changes (#315)

* feat: add to readme new keys

* feat: shoutout strix models, docs

* fix: mypy error

* fix: base api

* docs: update quickstart and models

* fixes: changes to docs

uniform api_key variable naming

* test: git commit hook

* nevermind it was nothing

* docs: Update default model to claude-sonnet-4.6 and improve Strix Router docs

- Replace gpt-5 and opus-4.6 defaults with claude-sonnet-4.6 across all docs and code
- Rewrite Strix Router (models.mdx) page with clearer structure and messaging
- Add Strix Router as recommended option in overview.mdx and quickstart prerequisites
- Update stale Claude 4.5 references to 4.6 in anthropic.mdx, openrouter.mdx, bug_report.md
- Fix install.sh links to point to models.strix.ai and correct docs URLs
- Update error message examples in main.py to use claude-sonnet-4-6

---------

Co-authored-by: 0xallam <ahmed39652003@gmail.com>

docs/contributing.mdx

@@ -32,7 +32,7 @@ description: "Contribute to Strix development"
   </Step>
   <Step title="Configure LLM">
     ```bash
-    export STRIX_LLM="openai/gpt-5"
+    export STRIX_LLM="anthropic/claude-sonnet-4-6"
     export LLM_API_KEY="your-api-key"
     ```
   </Step>