[codex] docs: align README version source of truth

[jeremymcs]

Summary

Closes #542

• Point the public README at @opengsd/gsd-core@latest / package.json as the current package version source of truth.
• Reframe archived release-note files and the changelog as continuity history instead of current release guidance.
• Clean localized README highlight sections and the docs index so stale legacy release and canary-current claims no longer compete with the npm/package metadata.

Root Cause

The README surface had inherited legacy release-note references from the pre-current package line, while @opengsd/gsd-core@latest and package.json now identify the active package version. That made the docs print conflicting version signals.

Validation

• npm view @opengsd/gsd-core version dist-tags --json confirmed latest: 1.2.0 and next: 1.2.0-rc.1.
• git diff --check
• GITHUB_BASE_REF=next npm run lint:docs -- --json
• Stale README/current-stream grep returned no matches for old release/canary claims.

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Note

Low Risk
Documentation-only wording and link changes; no runtime, auth, or data-handling code paths are modified.

Overview
Aligns public README and docs index copy so npm @opengsd/gsd-core / package.json is the single current version source, instead of stale docs/RELEASE-* or legacy highlight version numbers.

The English README updates the returning-user callout to recommend @latest, replaces the v1.42.1 release-note pointer with canonical-version guidance, and reframes CHANGELOG as history including archived notes. Localized READMEs (ja, ko, pt-BR, zh) rename version-tied highlight sections, drop v1.39.0 / canary workflow bullets, and add the same npm-first version note. docs/README.md removes per-release doc links, marks CANARY as archived maintainer notes, and points “what’s new” / preview streams at latest and next on npm.

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