Update .agent/workflows/build_and_validate.md

indent fenced code block

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Signed-off-by: Liam Girdwood <lgirdwood@gmail.com>

Author: lgirdwood

.agent/workflows/build_and_validate.md

@@ -7,13 +7,13 @@ This workflow describes the process for building and validating any new C code f
 **Note:** The QEMU build targets must be used for both building and testing.
 
 1. Build the new C code feature using the `xtensa-build-zephyr.py` script.
-```bash
-./scripts/xtensa-build-zephyr.py
-```
+    ```bash
+    ./scripts/xtensa-build-zephyr.py
+    ```
 
 2. Validate the feature with a ztest run using the `sof-qemu-run.sh` script.
-```bash
-./scripts/sof-qemu-run.sh
-```
+    ```bash
+    ./scripts/sof-qemu-run.sh
+    ```
 
 3. Ensure that all new features and functions have appropriate Doxygen comments and that the Doxygen documentation builds without errors or warnings.