docs(openspec): archive Cargo and release resolver changes

[Drswith]

Summary

Archive completed OpenSpec changes add-cargo-package-manager, fix-release-target-resolution after their implementation PRs merged, and close the agent-driven archive follow-up with repository validation.

Linked Artifacts

• Issue:
• ADR:
• OpenSpec: add-cargo-package-manager, fix-release-target-resolution
• Discussion:

Validation

• bun run openspec:validate
• bun run memory:check
• bun run lint
• bun run format:check
• bun run typecheck
• bun run test (if behavior changed)
• Not run, explained below

Release Intent

• Release: not applicable - OpenSpec archive closure only

Docs Updated

• Not needed
• docs/...
• openspec/...
• Follow-up issue or OpenSpec change created instead

Scope Check

• I did not add a new ad hoc root-level Markdown file.
• I updated the relevant issue, ADR, spec, runbook, or captured the missing doc work as follow-up.
• I did not silently expand project scope without recording it explicitly.

Closure Check

• Working tree was clean before archive closure started.
• Branch was pushed and this PR is the active delivery artifact.
• OpenSpec change is already archived or queued for agent-driven archive closure.
• Release is not applicable, delegated to release automation, or verified.

Notes

• Generated by bun run openspec:archive-closure.