[Bug]: Context compression breaks tool message chain, causing "role 'tool' must be a response to a preceding message with 'tool

#58327 Fixed P1 comp/agent

[Bug]: Context compression breaks tool message chain, causing "role 'tool' must be a response to a preceding message with 'tool_calls'" on strict providers

Context compression could orphan tool messages by dropping their assistant tool_calls message, causing HTTP 400 on strict providers like DeepSeek. Closed.