Update AGENTS.md

AGENTS.md

@@ -29,6 +29,28 @@ All code follows the patterns established in `src/wapp/`. The project prefix is
 | File-scope globals    | `_` + camelCase        | `_default_allocator`            |
 | File-scope constants  | SCREAMING_SNAKE        | `MAX_NODE_NAME`                 |
 
+### Formatting
+
+- **Indentation**: tabs (no spaces). Tab width is a viewer preference.
+- **Braces**: always required after `if`, `else`, `for`, `while`, `do` — even
+  when the body is a single statement. This avoids ambiguity and makes diffs
+  cleaner.
+
+```c
+// correct
+if (condition) {
+	do_thing();
+}
+
+for (int i = 0; i < n; i++) {
+	process(i);
+}
+
+// wrong — no braces, spaces instead of tabs
+if (condition)
+	do_thing();
+```
+
 ### Storage qualifiers
 
 Use the `wp_extern` / `wp_intern` / `wp_persist` aliases from wapp: