v4.2.1

docs(readme): add v4.2.1 Status + version-history entries to all 3 packages

CI publish workflow's documentation gate requires every queued package's
README.md to (a) have a Status block line starting with **\` on
public npmjs**and (b) a version-history line starting withv`.
Adding the 4.2.1 entries to all 3 packages so the CI gate passes on
re-tag.

• kadena-stoic-legacy: PATCH bump for triplet alignment, no code changes
• stoa-core: PATCH bump for triplet alignment, peer-dep on ksl 4.2.0->4.2.1
• ouronet-core: 23 new builders + 1 INFO reader + 1 unprotected read
  (full Phase-3b strategy-migration surface for OuronetUI v1.0.7)

Co-Authored-By: Claude Opus 4.7 (1M context) noreply@anthropic.com