baseplate 0.2.1

Shared substrate for agentic-harness tooling — model registry, trace types, path resolution, a cxpak MCP client, and Java-test detection
Documentation
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## What & why

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Closes #

## How it was verified

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## Checklist

- [ ] `cargo fmt --all -- --check` is clean
- [ ] `cargo clippy --all-targets -- -D warnings` has zero warnings
- [ ] `cargo test --locked` passes, and new/changed code is covered
- [ ] Docs updated in this PR if a documented surface changed (README, CONTRACT)
- [ ] Commits follow Conventional Commits and are logically scoped

## Notes for reviewers

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