chore: update Sonnet model references from 4.5 to 4.6

Update MODEL_SONNET constant and all documentation references
to reflect the new claude-sonnet-4-6 model version.

examples/statusline.json

@@ -13,7 +13,7 @@
       "C": "Cyan - username, todos",
       "T": "Gray - model name"
     },
-    "output_example": "affoon:~/projects/myapp main* ctx:73% sonnet-4.5 14:30 todos:3",
+    "output_example": "affoon:~/projects/myapp main* ctx:73% sonnet-4.6 14:30 todos:3",
     "usage": "Copy the statusLine object to your ~/.claude/settings.json"
   }
 }