[Rust port] Lockstep 2.0 release (TS 1.x final + cutover + npm deprecate)

[willwashburn]

Parent: #240

Context

Lockstep 2.0 release: cut the final TS 1.x, ship Rust binaries + crates + npm packages, deprecate the retired npm packages, document the migration. Single-day coordinated release — the orchestration, not the porting.

Scope

Pre-cutover

• Cut a final 1.x lockstep release of all 8 TS packages so anyone who can't migrate has a stable pin.
• Update root CHANGELOG.md with a migration note explaining the v2 transition.
• Update README.md to point at the Rust install paths.

Cutover day

Single GitHub Actions workflow that, in order:

1. Builds + tests the entire Cargo workspace.
2. Builds prebuilt burn binaries for darwin-arm64, darwin-x64, linux-arm64, linux-x64 (optionally win32-x64).
3. Publishes relayburn-sdk@1.0.0 and relayburn-cli@1.0.0 to crates.io (OIDC trusted-publisher).
4. Builds + publishes @relayburn/sdk@2.0.0 (umbrella) + per-platform packages (@relayburn/sdk-darwin-arm64, etc.) via the napi-rs CI matrix.
5. Builds + publishes relayburn@2.0.0 as a postinstall download shim that fetches the right burn binary from GitHub Releases.
6. Creates GitHub Release tagged v2.0.0 with the prebuilt binaries attached.

Post-cutover (same day)

• Run npm deprecate on the six retired packages with messages pointing at 2.0:
  • @relayburn/reader → "merged into @relayburn/sdk 2.0; internal Rust crate now"
  • @relayburn/ledger → same
  • @relayburn/analyze → same
  • @relayburn/ingest → same
  • @relayburn/mcp → "use burn mcp-server from the burn binary, or @relayburn/sdk for embedded MCP"
  • @relayburn/cli → "use the burn binary from the relayburn npm package or GitHub Releases"
• Don't unpublish — pinned consumers should keep working forever.

Wash bump

• Coordinate with wash team to bump to relayburn-sdk = "1" immediately after publish.

Decommission

• Remove packages/{reader,ledger,analyze,ingest,sdk,mcp,cli} from the repo. Only packages/sdk-node survives.
• Repo becomes a Cargo workspace with one TS subdirectory for the npm facade.
• Update CLAUDE.md to reflect the new layout.

Depends on

#241, #242, #243, #244, #245, #246, #247, #248

Acceptance

• Final TS 1.x lockstep release published.
• cargo install relayburn-cli on a clean machine produces a working burn binary.
• curl -fsSL <github-release-url> | tar xz produces a working burn binary on all 4 primary platforms.
• npm i -g relayburn on a clean machine downloads the right burn binary via postinstall.
• npm i @relayburn/sdk resolves the prebuilt napi-rs umbrella + correct platform package.
• All 6 deprecated packages show npm deprecation warnings with the messages above.
• Wash builds successfully against relayburn-sdk = "1".
• packages/{reader,ledger,analyze,ingest,sdk,mcp,cli} removed from the repo.
• Migration note merged into root CHANGELOG.md + README.md.
• gh issue close 218 (already closed, but cross-link to v2 SDK in a comment for posterity).