chore(release): bump to 0.6.1

[cssbruno]

Summary

• Bump the CLI and VS Code extension metadata to 0.6.1.
• Move the current changelog entry into v0.6.1 - 2026-06-16 and update the v0.6 release notes for the patch release.
• Refresh pinned install snippets and release workflow examples to v0.6.1.

Release Execution

• Published release: https://github.com/cssbruno/GoWDK/releases/tag/v0.6.1
• Release workflow: https://github.com/cssbruno/GoWDK/actions/runs/27639142970
• Artifact smoke workflow: https://github.com/cssbruno/GoWDK/actions/runs/27639703953

Verification

• node editors/vscode/scripts/sync-version.js --check
• go test ./cmd/gowdk -run Version
• go run ./cmd/gowdk version --json
• go build ./cmd/gowdk
• git diff --check
• Documented local release gates from docs/engineering/release.md
• gh workflow run release.yml --ref codex/release-0.6.1 -f version=v0.6.1
• gh workflow run release-smoke.yml --ref codex/release-0.6.1 -f version=v0.6.1

LLM Assistance

• Session summary: Codex prepared the 0.6.1 release metadata bump in a separate worktree, synced extension metadata from the CLI version constant, verified the release-bump checks, ran the documented local release gates, published v0.6.1, and verified release artifacts across Linux, macOS Intel, macOS ARM, and Windows.
• Human-reviewed assumptions: This is a patch release for the current 0.6 line and remains framed as experimental 0.x software, with no production-readiness claim.
• Follow-up work: Merge this PR so main reflects the published 0.6.1 release metadata.