feat(observe): add initial package structure and configuration for @flowiseai/observe (#6270)

* feat(observe): add initial package structure and configuration for @flowiseai/observe

- Introduced the @flowiseai/observe package with a modular architecture for observing AI agent executions and evaluations.
- Added essential files including ESLint and Prettier configurations, Jest setup, and TypeScript configuration.
- Created foundational components and documentation for usage, testing, and architecture.
- Updated pnpm-lock.yaml with new dependencies for the observe package.

This commit sets the groundwork for further development of the observability features.

* fix(observe): enhance documentation and improve execution polling logic

- Updated README.md to clarify the permissions required for the API token.
- Added cleanup logic in ExecutionDetail component to prevent memory leaks by removing event listeners on unmount.
- Improved clipboard copy functionality to check for navigator.clipboard availability.
- Adjusted useExecutionPoll hook dependencies to include fetchExecution for better stability.
- Enhanced unit tests for useExecutionTree and useObserveApi to ensure proper error handling and functionality.