[jcode] Orphaned web_search server_tool_use in history causes permanent 400 (session unrecoverable)

## Observed symptom Orphaned web_search server_tool_use in history causes permanent 400 (session unrecoverable) Summary A session's history ends up with a server-side `web_search` tool use that has no matching `web_search_tool_result`. From then on, every request to Anthropic fails with 400, and the session cannot continue. It happened early in the session (messages.5), so there was nothing to compact, and clearing the session was the only way out. Error `Anthropic API error (400 Bad Request): {"type":"error","error":{"type":"invalid_request_error","message":"messages.5: `web_search` tool use with id `srvtoolu_017Bq7tKmKKZJbMjWQucju` ## Literal error text ``` Anthropic API error (400 Bad Request): {"type":"error","error":{"type":"invalid_request_error","message":"messages.5: `web_search` tool use with id `srvtoolu_017Bq7tKmKKZJbMjWQucjurZ` was found without a corresponding `web_search_tool_result` block"}} ``` ## Environment GitHub 1jehuang/jcode #1638 ## Trigger / context Public GitHub report in 1jehuang/jcode (FRESH_7D). ## Source evidence - https://github.com/1jehuang/jcode/issues/1638 (2026-10-01T21:13:58Z) — evidence_class: PRIMARY_ISSUE_REPORT — #1638 ## Freshness - classification: FRESH_7D - retrieved_at: 2026-10-02T09:52:00.922591Z - scout_id: Cb110813942 ## Scout notes This Problem was published by the KFA Fresh Friction Scout from public sources. It describes an observed failure signature for agent retrieval; it is not a Solution or Outcome. Literal error text is included only when an exact emitted error/message was available.