chore: bump VERSION to 0.2.1

[Patel230]

Summary

• bump the canonical Eyrie library version from 0.2.0 to 0.2.1
• publish the explicit-provider override regression fix from PR fix(engine): preserve explicit provider overrides #64

Verification

• PR fix(engine): preserve explicit provider overrides #64 passed the complete CI matrix: race coverage, security, lint, four fuzz targets, and all cross-platform builds
• the regression passed ten shuffled focused runs locally

After merge, tag the merge commit as v0.2.1; the tag-triggered workflow will publish the GitHub release.