Track: full multi-version SDK docs (Mintlify versions)

[WomB0ComB0]

Context

Today the SDK docs at `sdks//api/` always reflect the latest `main`. Each generation overwrites the tree. As of #41, every generated SDK README carries a version stamp so users browsing the rendered docs can see which release is being described.

This issue tracks the larger follow-up: serving the docs for multiple versions in parallel.

When to do this

Defer until at least one SDK ships a v2 with breaking changes such that v1 users still need access to v1 docs. At v1.x, every release is the latest stable, so single-version docs are accurate.

Approach options

1. Mintlify `versions` in nav — duplicates the entire navigation tree per version. Heavy maintenance overhead but native support.
2. Versioned route prefixes — `sdks//api/v1/`, `sdks//api/v2/`. Pipeline writes to the version-specific path, and a redirect or selector points users at the latest by default. Lighter than option 1 but custom.
3. Versioned subdomain — `v1.docs.example.com` is a separate Mintlify deploy. Cleanest separation but two sites to keep in sync.

Migration prerequisites

• Decide on which SDKs need versioning vs always-latest (a CLI-only utility may never need versioned docs).
• Update each `api-docs..yml` template to write into the version-specific output path (or a `latest` alias).
• Update `scripts/splice-sdk-nav.py` and the in-template splice steps to write into the correct sub-group.
• Backfill: pick which historical tags to render, or accept v1+ from cutover only.

Out of scope for this issue

• Versioned guides / quickstarts / OpenAPI tab. The auto-generated SDK reference is the only thing changing fast enough to need versioning today.