v0.88.0

Added

• llmdialect/ir.BlockOpaque, a content block that carries one
  provider item verbatim for replay to the dialect that produced it:
  Block.Opaque holds an ir.Opaque with the producing Dialect, the
  item's Kind within it, and its JSON as Raw. A backend of that
  dialect writes Raw unchanged where the block stands; the other
  backends drop the block and record ir.LossOpaque (opaque), never an
  error. The lux dialect carries it both ways as {"type":"opaque", "opaque":{"dialect","kind","raw"}}, with raw as the JSON value
  itself, so a harness that stores sessions as lux JSON keeps the item
  byte for byte; luxsdk.Opaque and luxsdk.BlockOpaque re-export the
  vocabulary. Raw is kept in the form encoding/json writes (compact,
  with <, > and & escaped), which every later marshal leaves as it
  is; the lux decoder brings a body written by another encoder into that
  form. In a stream the block is one block_start whose header
  carries the payload, then its block_stop. The Anthropic, Chat and
  Responses frontends leave it out of the responses and streams they
  write, and the Anthropic stream shifts later content indices down past
  it so they stay dense. ir.PrefixCacheKeys hashes the block's
  dialect, kind and raw JSON after the fields every block contributes;
  keys of requests without opaque blocks are unchanged.
• llmdialect/ir.Request.ReasoningReplay asks for the model's reasoning
  in a form the next request of the conversation can carry back, which
  a reasoning model served over OpenAI Responses needs to keep its
  reasoning across turns. The openairesp backend then writes include: ["reasoning.encrypted_content"] (beside the logprobs member when that
  is asked too) and store: false, and keeps each reasoning item that
  comes back with encrypted_content as an opaque block of kind
  reasoning, from the response body and from the stream's
  response.output_item.done frame alike, after the summary's thinking
  block. Encoding a request replays such a block as its input item, and
  the thinking block right before it travels inside the item instead of
  being reported as thinking loss. A reasoning item without
  encrypted_content is not kept, so a caller that does not ask sees
  the same blocks and streams as before. The lux dialect carries the
  ask as reasoning_replay; the anthropic backend needs no ask, since
  its thinking blocks carry their signatures; the openaichat backend
  records ir.LossReasoningReplay (reasoning_replay).