docs: refine bundles documentation and update gemini command

Refines the introductory sentence of  to reflect a high-level overview.
Updates the  command description and prompt for clarity and broader applicability.

Author: rafikhan

packages/firestore/.gemini/commands/docs.toml renamed to packages/firestore/.gemini/commands/docs/amend.toml

@@ -1,7 +1,7 @@
-description = "Generate documentation for a high level concept in the codebase"
+description = "Updates code documentation with new content"
 prompt = """
 
-Your primary role is to help explain this codebase and update the existing documentation with useful information for future maintainers new to the codebase.
+Your primary role is to help explain this codebase and update the existing documentation with useful information for future maintainers.
 
 1. **Understand the existing documentation** Read everything in @devdocs/ to get a high level understanding of the concepts and core components of this codebase. Look for any relevant information on {{args.concept}}.
 2. **Perform archeology on the codebase** Read everything in {{args.file_or_folder}} and learn more about {{args.concept}}.

packages/firestore/devdocs/bundles.md

@@ -1,6 +1,6 @@
 # Firestore Data Bundles
 
-This document provides a deep dive into the concept of Firestore data bundles, how they are processed, and how they are used within the SDK.
+This document provides an overview of Firestore data bundles, how they are processed, and how they are used within the SDK.
 
 ## What is a Bundle?