docs: add AGENTS.md for block example guidelines

block-kit/AGENTS.md

@@ -0,0 +1,95 @@
+# Adding a Block Example
+
+A block example is **code-complete** when all four of these are present:
+
+1. Example file
+2. Test file
+3. README entry
+4. Correct docstring
+
+## Example file
+
+Create `src/main/java/blocks/{Type}.java`:
+
+```java
+package blocks;
+
+import com.slack.api.model.block.{Type}Block;
+import com.slack.api.model.block.Blocks;
+import com.slack.api.model.block.composition.BlockCompositions;
+
+/**
+ * {description from docs page — must match exactly}.
+ * {@link https://docs.slack.dev/reference/block-kit/blocks/{type}-block/}
+ */
+public class {Type} {
+    /**
+     * {Brief description of this specific example}.
+     */
+    public static {Type}Block example01() {
+        {Type}Block block = Blocks.{type}(b -> b. /* builder calls */ );
+        return block;
+    }
+}
+```
+
+Rules:
+- Package is always `blocks`
+- Each example is a `public static` method returning the block type
+- Methods named `example01()`, `example02()`, etc.
+- Use the `Blocks.*` builder DSL (not raw constructors)
+- Use `BlockCompositions.markdownText()` / `BlockCompositions.plainText()` for text objects
+- Use `BlockElements.*` for interactive elements
+- The class-level Javadoc first line must match the docs page `description` field exactly (found in the page's YAML frontmatter)
+
+## Test file
+
+Create `src/test/java/blocks/{Type}Test.java`:
+
+```java
+package blocks;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import com.google.gson.JsonParser;
+import com.slack.api.model.block.{Type}Block;
+import com.slack.api.util.json.GsonFactory;
+import org.junit.jupiter.api.Test;
+
+public class {Type}Test {
+    @Test
+    public void testExample01() {
+        {Type}Block block = {Type}.example01();
+        String actual = GsonFactory.createSnakeCase().toJson(block);
+        String expected = """
+            {
+              "type": "{type}",
+              ...
+            }
+            """;
+        assertEquals(JsonParser.parseString(expected), JsonParser.parseString(actual));
+    }
+}
+```
+
+The expected JSON must match the docs page example exactly (minus the outer `"blocks": [...]` wrapper).
+
+## README entry
+
+Add an entry to `block-kit/README.md` in alphabetical order under `### Blocks`:
+
+```markdown
+- **[{Name}](https://docs.slack.dev/reference/block-kit/blocks/{type}-block)**: {Description matching docs}. [Implementation](./src/main/java/blocks/{Type}.java).
+```
+
+The description must match the docs page `description` field exactly.
+
+## Build and verify
+
+```bash
+cd block-kit
+mvn compile   # compiles + runs Spotless formatter
+mvn test      # runs all tests including yours
+```
+
+Both must pass. Spotless (Palantir Java Format) runs automatically on compile — do not fight the formatter.