feat(api): establish the stable 1.0.0 release

[e54-bot]

Summary

• Set both workspace crates to 1.0.0, including the CLI's workshop-rs version requirement and lockfile.
• Document the one-time exact 1.0.0 version target and keep crates.io publication, canonical tagging, and GitHub Release creation on the existing release-plz and tag workflow.
• No Rust API or runtime behavior changes. The API freeze and downstream gates are complete in Freeze the workshop-rs public API for 1.0 #252.

Verification

• cargo fmt --all --check
• cargo metadata --locked --no-deps --format-version 1 — both packages and the CLI dependency resolve to 1.0.0
• cargo check --workspace --all-targets --locked
• cargo test --workspace --all-targets --locked — 373 passed, 3 ignored
• cargo clippy --workspace --all-targets -- -D warnings
• cargo run --locked -p workshop-rs --bin workshop-catalog-gen -- check
• git diff --check

The existing Public API compatibility check and hosted CI remain required on this PR.