[Feature] Add Exposures + Semantic Layer visibility to VS Code Catalog

### Before you submit

- [x] I have searched the existing issues and could not find a duplicate
- [x] I am requesting an extension of existing dbt Fusion functionality, not a Big Idea better suited to a [Discussion](https://github.com/dbt-labs/dbt-fusion/discussions)

### Which component does this feature relate to?

VS Code extension

### Describe the feature

The new VS Code Catalog experience is a fantastic step toward making dbt feel like a true Analytics Engineering IDE.

One major enhancement that would make the experience even more powerful would be surfacing:

Exposures
Semantic Models
Metrics
Downstream lineage visibility
Blast radius analysis

directly inside the Catalog panel.

Why this matters

Today, developers can already view:

columns
tests
documentation
model metadata

inside VS Code.

Adding downstream business context would complete the workflow by helping engineers understand:

which dashboards depend on a model
which executive reports are impacted
which semantic entities consume the data
ownership/governance context
business criticality
Example workflow

If I open:

mart_revenue

I’d love to immediately see:

Tableau Executive Dashboard exposure
Semantic model dependencies
Metrics consuming the mart
Criticality/maturity metadata
Downstream lineage graph

This would significantly improve:

impact analysis
governance workflows
developer productivity
enterprise-scale dbt operations

Especially for large Analytics Engineering teams managing governed data products.

### Describe alternatives you've considered

Currently the main alternative is switching between:
- VS Code
- dbt Docs
- dbt Cloud
- BI tools
- lineage/catalog platforms

to manually understand downstream dependencies and governance context.

Another option is relying on external metadata/catalog tools, but this creates additional context switching during development.

Surfacing exposures, semantic models, and downstream lineage directly in the VS Code Catalog would centralize the workflow and reduce friction for Analytics Engineers working inside dbt projects.

### Who will this benefit?

This would benefit:
- Analytics Engineers
- Data Engineers
- BI Developers
- Analytics Architects
- Governance teams
- Platform teams

Especially organizations operating large enterprise dbt deployments with:
- multiple marts
- semantic layers
- governed metrics
- executive dashboards
- data product ownership models

The feature would improve:
- impact analysis
- debugging
- onboarding
- code reviews
- governance workflows
- metadata discoverability

It would be particularly valuable for teams practicing modern Analytics Engineering and data product development at scale.

### Are you interested in contributing this feature?

Happy to provide feedback, testing, workflow examples, and enterprise Analytics Engineering use cases if helpful.

### Anything else?

Really excited about the direction of the VS Code Catalog experience overall.

The current workflow already feels much closer to a true Analytics Engineering IDE compared to traditional SQL development workflows.

Adding downstream business context (exposures, semantic models, metrics, lineage impact) would make the development experience even more powerful for enterprise dbt teams.