Tool response images break Anthropic tool_result grouping on OpenAI-compatible providers

[katzdave]

Initial report from @spencrmartin using Opus 4.6 on databricks.

When multiple tool calls return images, the OpenAI-compatible format layers (databricks, openai)
split each image into a separate user message since role: "tool" only supports strings. This
interleaves user image messages between tool messages, violating Anthropic's requirement that all
tool_result blocks appear consecutively after the assistant message.

assistant: tool_calls=[A, B, C]
tool: A
user: A's image ← breaks consecutive tool group
tool: B
user: B's image
tool: C

Error: tool_use ids were found without tool_result blocks immediately after

Affects any provider proxying to Anthropic via OpenAI-compatible API (Databricks,
OpenRouter→Claude, etc.).

Confirmed from diagnostic bundle: 4 tool_calls in one assistant message, 3 responses from
image_processor containing image data.

A proposed fix (#7393) exists that reorders the formatted messages to defer image messages until after the
tool group, but needs careful review — it modifies the message array after formatting which could
have unintended side effects.