docs: distribute package-specific GEMINI.md context to each package (#22734)

packages/sdk/GEMINI.md

@@ -0,0 +1,18 @@
+# Gemini CLI SDK (`@google/gemini-cli-sdk`)
+
+Programmatic SDK for embedding Gemini CLI agent capabilities into other
+applications.
+
+## Architecture
+
+- `src/agent.ts`: Agent creation and management.
+- `src/session.ts`: Session lifecycle and state management.
+- `src/tool.ts`: Tool definition and execution interface.
+- `src/skills.ts`: Skill integration.
+- `src/fs.ts` & `src/shell.ts`: File system and shell utilities.
+- `src/types.ts`: Public type definitions.
+
+## Testing
+
+- Run tests: `npm test -w @google/gemini-cli-sdk`
+- Integration tests use `*.integration.test.ts` naming convention.