Add and update README files

- Adds a detailed README.md to the `packages/cli` directory covering build, run, and debug instructions specific to the CLI package.
- Updates the root README.md with comprehensive project information, including cloning instructions (Gerrit), monorepo build/run/debug steps, and references to relevant resources.

Created by yours truly: __Gemini Code__

packages/cli/README.md

@@ -0,0 +1,34 @@
+# Gemini Code CLI
+
+This package contains the core command-line interface for Gemini Code.
+
+## Building
+
+To build only the CLI package, navigate to this directory (`packages/cli`) and run:
+
+```bash
+npm run build
+```
+
+This command executes the TypeScript compiler (`tsc`) as defined in this package's `package.json`. Ensure dependencies have been installed from the root directory (`npm install`) first.
+
+## Running
+
+To start the Gemini Code CLI directly from this directory:
+
+```bash
+npm start
+```
+
+This command executes `node dist/gemini.js` as defined in this package's `package.json`.
+
+## Debugging
+
+To debug the CLI application using VS Code:
+
+1.  Start the CLI in debug mode from this directory (`packages/cli`):
+    ```bash
+    npm run debug
+    ```
+    This command runs `node --inspect-brk dist/gemini.js`, pausing execution until a debugger attaches.
+2.  In VS Code (opened at the root of the monorepo), use the "Attach" launch configuration (found in `.vscode/launch.json`). This configuration is set up to attach to the Node.js process listening on port 9229, which is the default port used by `--inspect-brk`.