v1.0.0 docs: finalize release changelog

[tiagolauer]

Summary

• promote the existing [Unreleased] notes to 1.0.0, dated 2026-08-20
• leave a new empty [Unreleased] section for subsequent work
• document that published core and plugin packages include their MIT license

Verification

• npm test: 225 passed
• architecture fitness checks passed
• npm run test:perf: 134,857 instantiations against the 150,000 ceiling; Next delta +22 (+0.04%)
• npm run test:package passed
• package dry runs confirmed LICENSE in both workspace tarballs
• npm audit: 0 vulnerabilities
• no existing v1.0.0 tag, GitHub Release, or npm version collision

Review

• test coverage: 100% of 0 new executable paths; no tests needed
• plan completion: 1/1 item complete
• pre-landing and adversarial reviews: no remaining findings

Scope

Documentation only. No runtime, compiler, package version, plugin version, or public API behavior changed.

Do not dispatch the Release workflow until the remaining release-readiness steps are complete.