chore(release): prepare pgdumpx 0.2.0

[tappe9]

Summary

• prepare pgdumpx and pgdumpx-cli 0.2.0 as the first public release
• add complete crates.io metadata, package-content checks, and staged publication recovery guidance
• verify the packaged workspace, installed CLI contract, library dry-run, and release notes without publishing or tagging

Verification

• python3 scripts/test-release-readiness.py
• python3 scripts/verify-release-packaging.py
• exact-head CI, Release Packaging, and Dependency Advisories succeeded for a5c9bb8a53778e9659e23a9882064d962f926a23

Scope

• no archive parser, compression, extraction, row scanning, or command behavior changes
• actual crates.io publication, tag creation, and GitHub Release creation remain credential-gated

Closes #92