* First integration of at commands into useGeminiStream.ts
* feat: Integrate @ command for file/directory reading
- Adds support for `@<path>` commands in the CLI UI to read file or directory contents using the `read_many_files` tool.
- Refactors `useGeminiStream` hook to handle slash, passthrough, and @ commands before sending queries to the Gemini API.
- Improves history item ID generation to prevent React duplicate key warnings.
* fix: Handle additional text after @ command path
- Modifies the `@` command processor to parse text following the file/directory path (e.g., `@README.md explain this`).
- Includes both the fetched file content and the subsequent text in the query sent to the Gemini API.
- Resolves the TODO item in `atCommandProcessor.ts`.
* feat: Allow @ command anywhere in query and fix build
- Update `atCommandProcessor` to correctly parse `@<path>` commands regardless of their position in the input string using regex. This enables queries like "Explain @README.md to me".
- Fix build error in `useGeminiStream` by importing the missing `findSafeSplitPoint` function.
* rename isPotentiallyAtCommand to isAtCommand
* respond to review comments.
* Refactor useGeminiStream to pull slash commands and passthrough commands into their own processors.
* whitespace lint errors.
* Add sugestions from code review.
