docs: enhance provider configuration documentation with Anthropic examples

Add comprehensive examples for custom Anthropic-compatible provider configuration
including thinking budget options and realistic configuration patterns.

* Add Anthropic-compatible provider example with thinking configuration
* Enhance existing custom provider example with reasoningEffort option
* Remove unnecessary code block line highlighting for cleaner examples
* Improve documentation coverage for advanced provider options

Author: no1wudi

packages/web/src/content/docs/providers.mdx

@@ -1317,7 +1317,7 @@ You can use any OpenAI-compatible provider with opencode. Most modern AI provide
 
 Here's an example setting the `apiKey`, `headers`, and model `limit` options.
 
-```json title="opencode.json" {9,11,17-20}
+```json title="opencode.json"
 {
   "$schema": "https://opencode.ai/config.json",
   "provider": {
@@ -1334,6 +1334,9 @@ Here's an example setting the `apiKey`, `headers`, and model `limit` options.
       "models": {
         "my-model-name": {
           "name": "My Model Display Name",
+          "options": {
+            "reasoningEffort": "high"
+          },
           "limit": {
             "context": 200000,
             "output": 65536
@@ -1345,6 +1348,35 @@ Here's an example setting the `apiKey`, `headers`, and model `limit` options.
 }
 ```
 
+For Anthropic-compatible providers:
+
+```json title="opencode.json"
+{
+  "$schema": "https://opencode.ai/config.json",
+  "provider": {
+    "anthropic-provider": {
+      "npm": "@ai-sdk/anthropic",
+      "name": "My AI ProviderDisplay Name",
+      "options": {
+        "baseURL": "https://api.myprovider.com/v1",
+        "apiKey": "{env:ANTHROPIC_API_KEY}"
+      },
+      "models": {
+        "my-model-name": {
+          "name": "My Model Display Name",
+          "options": {
+            "thinking": {
+              "type": "enabled",
+              "budgetTokens": 8000
+            }
+          }
+        }
+      }
+    }
+  }
+}
+```
+
 Configuration details:
 
 - **apiKey**: Set using `env` variable syntax, [learn more](/docs/config#env-vars).