Document the current theme packages and Rust usage

[konojunya]

Background

The README used future-tense ownership, did not show how to consume the Rust catalog, and left generated package READMEs on older catalog versions. It also did not distinguish the published Cargo crate from the repository-only JavaScript package tree.

Implementation Approach

• Describe current repository ownership in the present tense.
• Add a minimal stack-theme catalog example and docs.rs link.
• State which artifact is publicly distributed and how browser consumers receive the catalog.
• Synchronize the Cargo and JavaScript package READMEs with catalog 0.6.0.

Testing Approach

• npm run validate
• npm run generate:check
• npm test
• npm run typecheck
• cargo test --workspace --locked
• cargo doc --workspace --no-deps --locked
• Compiled and ran the README example in an isolated Cargo project.

Review Perspectives / Points of Concern

Please verify that the distribution section clearly distinguishes generated package parity from a standalone public npm release.