refactor(compiler): migrate to workshop-rs 0.7.0

[e54-bot]

Summary

• Bump workshop-rs to =0.7.0.
• workshop-rs 0.7.0 marks Rule non_exhaustive; build rules through Rule::new (private rule_from_parts helper) at the 7 lowering sites. OPY semantics unchanged.

Verification

• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets --all-features -- -D warnings
• cargo test --workspace --all-targets --all-features (434 passed, 1 ignored in main suite)
• python3 -m unittest discover -s tools/overpy/tests (37 passed)
• Oracle compatibility gate and probe_builtins not run: no lowering/optimization/builtin-argument behavior changed.

Release gate

Refs #359. The final workshop-rs 1.0 candidate is not published; rerun the consumer gates against it before closing #359 and reporting on wrightkit/workshop-rs#252.