Model documentation / data dictionary view in VS Code extension

## Feature Request

Add the ability to view rendered documentation for a model directly within the VS Code extension — a "data dictionary" panel that displays a model's column schema (names, types, descriptions) in a formatted, readable view.

## Context

Users want to quickly reference column-level documentation (names, data types, descriptions) for a model without leaving VS Code. Competing VS Code extensions for dbt already offer a similar experience, and users are requesting parity.

## Expected Behavior

- From a model file (or via a command/sidebar), open a formatted view showing:
- Column names
- Column data types
- Column descriptions (from `schema.yml` / docs blocks)
- The view should render cleanly (not raw YAML) — think `dbt docs` style but inline in the editor.