v0.11.9

Real-time robustness and a new API reference

Streaming against the real-time source now survives replica turnover, head
reporting is correct for datasets whose variants finalize independently, and the
API reference at /docs has been rebuilt around what a consumer needs first.

• Replica turnover is no longer client-visible. A real-time request whose connection dies before any response byte arrives is replayed once, instead of surfacing as an error while a healthy sibling sits idle behind the same address. Nothing already delivered is ever duplicated.
• Correct head for datasets that finalize independently. The portal advertises the lower of the available finalized heads, so a stream no longer waits on — or comes back empty for — a head that has not finalized for the data it asked for. (#128)
• Head falls back to archival data when the real-time head is unavailable, instead of reporting none. (#129)
• New API reference at /docs, replacing Swagger UI: an orientation to the finalized vs. real-time data model, the fork-handling protocol, and a first-query walkthrough. Internal endpoints are filtered out of the published spec, and the served version now tracks the release. (#114)
• x-request-id is now echoed. The echo layer was attached where it wrapped no routes, so it had never run.

See spec/README.md for the Portal's behavioral contract, invariants, and conformance plan — new in this release.

Full Changelog: v0.11.8...v0.11.9