Release version 0.2.1

[Ismail-elkorchi]

What

• set the npm, lockfile, and JSR manifests to 0.2.1
• move the accumulated unreleased changes into the 0.2.1 changelog section

Why

The registry release remains at 0.2.0 while main contains the release-verification and runtime-contract fixes merged in PRs #164–#166. npm versions are immutable, so consumers need a new patch release.

Impact

This pull request changes release metadata only. Publishing v0.2.1 from the merged commit will make the existing post-0.2.0 runtime fixes available through npm and JSR.

Verification

• npm run release:notes:dry-run
• npm run changelog:update:dry-run
• npm run qualification:performance
• full release profile: conformance, cross-runtime, browser, package, serialization, fragments, fuzz, resource, mutation, and supply-chain gates passed locally; one repeated local performance sampling pass rejected host-load spread while the isolated exact-commit performance run passed, so the clean hosted performance check remains required before merge