Lineage panel blank for models with high upstream count (regression in 0.61.7)

**Description**

After upgrading to 0.61.7, the lineage panel renders blank for certain models. Downgrading to 0.61.6 fixes the issue.

**Steps to reproduce**

1. Open a model with `upstreamCount` of ~31 or higher in the lineage panel
2. Observe blank lineage panel — no graph rendered, no error message shown

**Expected behaviour**

Lineage graph renders as it did in 0.61.6.

**Actual behaviour**

Blank lineage panel. The following error appears in the webview console (Help → Toggle Developer Tools → Console):

Uncaught (in promise) TypeError: Cannot read properties of undefined (reading 'id')
at gH (main.js:306:11186)
at Ab (main.js:6412:12358)
at main.js:6412:88800

The extension log (`Lineage:getStartingNode:No event found`) fires repeatedly on every click but no rendering error is surfaced to the user.

**Environment**

- Extension version: 0.61.7 (regression from 0.61.6)
- OS: macOS (darwin-arm64)
- dbt version: 1.10.8
- Adapter: BigQuery
- `dbt.enableNewLineagePanel: true`

**Workaround**

Downgrade to 0.61.6.