chore: import upstream snapshot with attribution

strix/tools/apply_patch/README.md

@@ -0,0 +1,10 @@
+# apply_patch
+
+SDK-provided file patching tool — the agent's only first-class way to edit
+files in the sandbox. Surfaced to the model as `patch` (renamed via
+`_TOOL_NAME_OVERRIDES` in `strix/agents/factory.py`).
+
+- **Implementation:** `agents.sandbox.capabilities.tools.apply_patch_tool.ApplyPatchTool`
+  (upstream `agents` SDK)
+- **Wired in:** `strix/agents/factory.py` — added per-run via the SDK
+  `Filesystem` capability.