feat(remote): stream Git-style upload bundles for clone

[mayneyao]

Summary

• add optional upload-bundle protocol support that streams a stable ref snapshot and immutable objects in one response
• make clone consume the bundle through a temporary local remote, with 404/405 fallback to the legacy transport
• prefetch Cloudflare R2 objects with a bounded window of 8
• prepare @eidos.space/graft-remote packages 0.2.0 and @eidos.space/graft SDK 0.3.1

Performance

Staging clone of the same repository improved from a 16.61s client median to 6.85s, while Worker time improved from 13.31s to 2.76s. All runs produced the same head, 63 commits, and 345 paths.

Verification

• just test: 618 passed, 1 skipped; doctests and SQL tests passed
• pnpm check:remote and pnpm test:remote: 24 tests passed
• pnpm test:remote-release: 6 tests passed
• Remote archive prepare, verify, and publish dry-run passed for 0.2.0
• Cloudflare Worker deploy dry-run passed
• docs build passed
• local SDK release build and 14 Node tests passed for 0.3.1
• cargo fmt --check and targeted cargo clippy passed; only pre-existing warnings remain outside this diff

Review

Pre-Landing Review: No issues found. The optional Codex CLI review could not run because its local native binary is missing; manual critical and informational checklist passes were completed.