docs(sdk): add GPT-5 preset example page linking to code

sdk/guides/gpt5-preset.mdx

@@ -0,0 +1,35 @@
+---
+title: GPT-5 Preset (ApplyPatchTool)
+description: Use the GPT-5 preset to enable ApplyPatchTool-based file editing as an opt-in alternative, mirroring the Gemini preset approach.
+---
+
+<Note>
+This example is available on GitHub: [examples/01_standalone_sdk/35_gpt5_apply_patch_preset.py](https://github.com/OpenHands/software-agent-sdk/blob/main/examples/01_standalone_sdk/35_gpt5_apply_patch_preset.py)
+</Note>
+
+The GPT-5 preset provides an optional tool bundle that replaces the standard claude-style FileEditorTool with ApplyPatchTool, following the same pattern as the Gemini preset. This allows you to explicitly opt into ApplyPatch-based editing without changing any global defaults.
+
+```python icon="python" expandable examples/01_standalone_sdk/35_gpt5_apply_patch_preset.py
+# See linked file for the full example.
+```
+
+## Running the Example
+
+```bash
+export OPENAI_API_KEY="your-api-key"  # or set LLM_API_KEY
+# Optionally select a model, e.g. a mini variant if available
+# export LLM_MODEL="openai/gpt-5.2-mini"  # fallback: openai/gpt-5.1-mini or openai/gpt-5.1
+cd agent-sdk
+uv run python examples/01_standalone_sdk/35_gpt5_apply_patch_preset.py
+```
+
+## Why this preset?
+
+- Mirrors the Gemini preset approach (opt-in, not default)
+- Uses ApplyPatchTool for unified, patch-based edits preferred for GPT-5
+- Works with existing SDK agent flow (get_gpt5_agent)
+
+## Related
+
+- **Gemini preset** approach is documented in its PR; you can adopt it similarly by calling `get_gemini_agent`.
+- **Default preset**: unchanged; continues to use FileEditorTool unless you opt into this preset.