buildRequest now tracks a source-index → built-message-index mapping
during the role-merge pass, then uses the mapping to attach
cache_control: {type: ephemeral} markers at the positions indicated by
Request.CacheHints. The last tool, the last system part, and the last
non-system message each get a marker when the corresponding hint is set.
Covers the merge-induced index drift that would otherwise cause the
breakpoint to land on the wrong content block when consecutive same-role
source messages are combined into a single Anthropic message with
multiple content blocks.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Removes the blank-assign workaround that was only needed because the
anth import was being kept alive for Task 5's use. Task 5 will bring
the import back when it actually references anth.CacheControlTypeEphemeral.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Switches buildRequest to emit anthReq.MultiSystem instead of anthReq.System
whenever a system message is present. Upstream's MarshalJSON prefers
MultiSystem when non-empty, so the wire format is unchanged for requests
without cache_control. This refactor is a prerequisite for attaching
cache_control markers to system parts in the next commit.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
