feat(turbopuffer): add the Turbopuffer SDK

[Mkassabov]

Caution

STOP — there is already an open distilled PR for Turbopuffer by someone else. Distilled's generator pipeline has changed a lot; this is a new implementation, not a rebase of theirs. Review both and do not merge this and theirs blindly.

• @agcty — feat(turbopuffer): add @distilled.cloud/turbopuffer SDK #357

This is the requested Turbopuffer SDK. distilled#357 is an existing Turbopuffer SDK PR (not an issue); this PR is a new generator-pipeline implementation of the same request.

Adds @distilled.cloud/turbopuffer, generated from a first-party API description.

• Related PR: feat(turbopuffer): add @distilled.cloud/turbopuffer SDK #357
• Fetch script: stacks/distilled-submodules/spec-repos/turbopuffer/fetch-specs.ts
• Spec source: https://raw.githubusercontent.com/turbopuffer/turbopuffer-openapi/next/openapi.yml
• Convert/generate: packages/turbopuffer/scripts/{convert,generate}.ts
• Mirror repo distilled-mirror/spec-mirror-turbopuffer is created by the distilled-submodules stack on merge to main. Until then, regenerate with pnpm specs:local turbopuffer and DISTILLED_SPECS_LOCAL=1 pnpm generate turbopuffer.

pnpm specs:link turbopuffer recorded the .gitmodules stanza (shallow = true).