You are an expert frontend engineer and product designer. Extend the existing **Jupyter-like deep research notebook** prototype with advanced capabilities for **tool integration**, **human checkpoints**, and **traceability**.
### New Requirements
#### 1. Tool Integration
* Support connecting each cell to **external tools or APIs**, such as:
* MCP (Model Context Protocol) services.
* Research or data APIs (e.g., arXiv, PubMed, financial data).
* Custom backend endpoints.
* Each cell may declare:
```json
{
"tools": ["search_api", "data_cleaner", "plot_generator"]
}
```
* When a cell runs, it may show:
* Which tools were invoked.
* Input/output logs for each tool.
* API call status, latency, and result preview.
* Allow users to **configure tool parameters** or **reconnect tools** via a modal.
#### 2. Human Checkpoints
* Enable **human-in-the-loop review** for specific cells or workflow stages:
* Cells can be marked as “🧍 Human Checkpoint Required”.
* The system pauses execution until the user verifies or edits the intermediate result.
* Human reviewers can:
* Approve/Reject the result.
* Add comments or corrections inline.
* Re-run or reassign the cell to an …
Create an app for a **deep research product** that functions like a **Jupyter notebook**, where each **agent or reasoning step** lives in its own **cell**.
### Core Concept
* Each cell represents one **agent** or **processing step** (e.g., researcher, analyst, summarizer).
* A cell contains:
* Agent name or type
* Input prompt or references to previous cells
* Executable/re-runnable action button
* Structured output (text, markdown, table, chart, or JSON preview)
* The output of each cell can be passed as input to subsequent cells.
* Cells can be re-run independently to fix errors, fetch updated information, or explore variations.
### Features
1. **Notebook Layout**
* Vertical stack of cells, visually resembling a Jupyter notebook.
* Each cell shows:
* Agent header with name/icon.
* Editable input area.
* “Run” button.
* Output viewer (auto-formatted by type).
* Optional add/delete/reorder of cells.
2. **Output Visualization**
* Support multiple types of outputs:
* **Text/Markdown** → rendered in formatted text.
* **Tables/DataFrames** → rendered as interactive tables.
* **Ch…
