feat: rewrite gh-commit in Go with local Ollama backend

Replaces the Python/Crush/DuckDB implementation with a CGO-free Go binary:
cobra CLI, modernc.org/sqlite storage, huh/lipgloss UI, and speed-tuned raw
/api/generate calls (think:false, keep_alive, capped num_predict) against a
local qwen3.5:2b. Ships as a gh extension via cli/gh-extension-precompile.

crush-provider/crush.json

@@ -1,18 +0,0 @@
-{
-  "$schema": "https://charm.land/crush.json",
-  "providers": {
-    "groq": {
-      "type": "openai-compat",
-      "base_url": "https://api.groq.com/openai/v1",
-      "api_key": "$GROQ_API_KEY",
-      "models": [
-        {
-          "id": "openai/gpt-oss-120b",
-          "name": "GPT-OSS 120B on Groq",
-          "context_window": 131072,
-          "default_max_tokens": 8192
-        }
-      ]
-    }
-  }
-}