Images produced by tools (extensions, MCP bridges, screenshot tools) went into
session history at full resolution because processImage was only wired to the
read tool and @file CLI attachments. Providers validate every image in the
request, so one oversized image poisons the whole conversation: Anthropic drops
its per-image cap from 8000px to 2000px once a request carries many images, and
every later turn re-sends the same payload. Switching models does not help.
Normalize tool result images in AgentSession.afterToolCall, after the extension
tool_result hook so extension-injected images are covered too. Honors
images.autoResize, and keeps the original block when processing fails so an
unavailable image backend does not delete tool output.
Refs #5369
Assisted-By: devx/86bf3b09-9aba-4d03-8154-50fca3ffc9b5
