fix(eol): expose dependency summary on scan components

[facundo-herodevs]

Summary

• Add the missing DependencySummary contract already returned by eol-api.
• Require EolScanComponent.dependencySummary while allowing null when the SBOM dependency graph cannot be parsed.
• Add compile-time contract coverage and document the exported type and null semantics.

Changes

File	Change
src/types/eol-scan.ts	Adds DependencySummary and declares EolScanComponent.dependencySummary as DependencySummary | null.
src/types/eol-scan.test.ts	Verifies the API contract shape, nullability, and that the component field is required.
README.md	Documents the new export and distinguishes unknown classifications from a null summary.

Review notes

This aligns the shared TypeScript contract with the existing report payload. It does not add or change runtime behavior.

Verification

• npm run lint (Node 24)
• npm run format:check (Node 24)
• npm run type-check (Node 24)
• npm run test (Node 22 and 24)
• npm run build (Node 22 and 24)

Related to neverendingsupport/evergreen-ui#429