feat: enable rust core by default and add non-rust e2e smoke

[jy-tan]

Summary

Default Rust core usage to on (with fail-open fallback) in the Node SDK, add startup visibility for Rust/fallback state, and add a dedicated non-Rust E2E smoke test to ensure JavaScript fallback paths keep working. Also bump the core binding dependency to drift-core-node 0.1.7.

Changes

• Make TUSK_USE_RUST_CORE default to enabled when unset, with explicit truthy/falsy parsing (1/true/yes/on and 0/false/no/off) and safe handling of invalid values.
• Add startup status logging in SDK initialization to report Rust enabled/disabled/fallback decisions and binding load errors.
• Add a dedicated non-rust-smoke E2E workflow job (http) that runs with TUSK_USE_RUST_CORE=0.
• Bump @use-tusk/drift-core-node from 0.1.6 to 0.1.7 in package.json and package-lock.json.
• Update Rust-core docs/environment variable docs to reflect default-on behavior, fallback logging, and compatibility-matrix linkage.

[cubic-dev-ai]

No issues found across 7 files