feat: add resident Node.js SDK

[mayneyao]

Summary

• expose a long-lived Rust repository session backed by the existing RepositoryCommandService and official remotes
• publish the ABI-stable Node-API package as @eidos.space/graft, with explicit in-memory HTTP credentials and stable lifecycle/error semantics
• add five-platform build/test/package/release automation, performance evidence, architecture docs, and Graft v0.9.0 release metadata

Materialization contract

restore, pull, and cloneRepository can replace worktree files. Eidos must close affected application SQLite handles before those calls and reopen them afterward. Other SDK operations do not materialize tracked worktree files.

Validation

• just test: 585 Rust tests, 82 doctests, all SQL tests
• cargo test -p graft-sdk --locked: 9 passed
• strict targeted clippy and cargo fmt --all --check
• Node 24 integration: 8 passed; Node 20 compatibility: 6 passed, 2 node:sqlite-only skipped
• native macOS arm64 build and root + five platform npm package assembly/dry-pack
• docs build: 77 pages
• actionlint and frozen lockfile/package metadata checks

Release

After merge, publish annotated v0.9.0 and graft-sdk-v0.1.0 tags. The SDK workflow publishes platform packages before the root package, creates checksummed GitHub assets, and verifies public installs on every supported target.

No production deployment is part of this PR.