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

GEMINI.md

@@ -22,9 +22,10 @@ powerful tool for developers.
     rendering.
   - `packages/core`: Backend logic, Gemini API orchestration, prompt
     construction, and tool execution.
-  - `packages/core/src/tools/`: Built-in tools for file system, shell, and web
-    operations.
   - `packages/a2a-server`: Experimental Agent-to-Agent server.
+  - `packages/sdk`: Programmatic SDK for embedding Gemini CLI capabilities.
+  - `packages/devtools`: Integrated developer tools (Network/Console inspector).
+  - `packages/test-utils`: Shared test utilities and test rig.
   - `packages/vscode-ide-companion`: VS Code extension pairing with the CLI.
 
 ## Building and Running
@@ -58,10 +59,6 @@ powerful tool for developers.
 
 ## Development Conventions
 
-- **Legacy Snippets:** `packages/core/src/prompts/snippets.legacy.ts` is a
-  snapshot of an older system prompt. Avoid changing the prompting verbiage to
-  preserve its historical behavior; however, structural changes to ensure
-  compilation or simplify the code are permitted.
 - **Contributions:** Follow the process outlined in `CONTRIBUTING.md`. Requires
   signing the Google CLA.
 - **Pull Requests:** Keep PRs small, focused, and linked to an existing issue.
@@ -69,8 +66,6 @@ powerful tool for developers.
   `gh` CLI.
 - **Commit Messages:** Follow the
   [Conventional Commits](https://www.conventionalcommits.org/) standard.
-- **Coding Style:** Adhere to existing patterns in `packages/cli` (React/Ink)
-  and `packages/core` (Backend logic).
 - **Imports:** Use specific imports and avoid restricted relative imports
   between packages (enforced by ESLint).
 - **License Headers:** For all new source code files (`.ts`, `.tsx`, `.js`),