Phase 8: v1.0 release candidate validation + tag publication

[JRedeker]

Summary

Final release candidate validation: smoke-test goreleaser pipeline, verify cross-platform builds, tag v1.0.0-rc1, validate release artifacts.

Why

All implementation phases (0–7) are archived and merged. Phase 8 polish is the final gate before v1.0 release.

Acceptance Criteria

• go test ./... passes on linux/amd64 and darwin/arm64
• go vet ./... clean
• gofmt -d . clean
• goreleaser snapshot build succeeds
• Tag v1.0.0-rc1 pushed
• GitHub Release created with binary artifacts
• oca install works on fresh system using released binary

Proposal

docs/proposals/phases.md § Phase 8

WSJF Estimate

Value: 10 | TC: 10 | RROE: 10 | Effort: 3 | WSJF: 10.0