* fix(agent-core): route image-compression captions through hidden system reminders
Prompt ingestion (server upload/base64 route, TUI paste, ACP) annotates a
compressed image with an inline <system> caption inside the user's own
message. That raw markup rendered verbatim in every user-visible history
projection (TUI session replay, web UI) and leaked into session titles.
Split the caption out at the appendUserMessage chokepoint and deliver it
through the built-in system-reminder injection (origin
{kind: 'injection', variant: 'image_compression'}), which every UI already
hides. The model still receives the full note; ingestion sites and the wire
protocol are unchanged. Session titles/lastPrompt strip the caption the same
way. Tool-result captions (MCP) keep the established <system> convention.
Covered by unit tests plus an end-to-end smoke suite that drives
rpc.prompt/steer through the real turn pipeline and asserts the provider
wire request, stored history, replay records, and resume parity.
* chore: tighten changeset wording per gen-changesets conventions
175b95f3af