Support parsing: .NET published runtime artifacts (runtimeconfig.json, assembly metadata)

[mstykow]

Provenant already parses .deps.json via issue #117, but the broader published-runtime surface remains untracked in GitHub.

Scope

• *.runtimeconfig.json
• bounded published .NET runtime/app metadata that materially affects package or runtime identity
• assembly metadata that belongs to published runtime artifacts

Why this matters

Published .NET applications ship structured runtime metadata that can expose package identity, runtime configuration, and dependency context even when source manifests are absent.

Notes

This issue captures the remaining future work that had been grouped under a broader roadmap row. It should not reopen .deps.json, which is already implemented and closed under #117.