fix: drop a broken 5.5 thinking chain

[dofastted]

Summary

• Opus / Sonnet / Haiku 5.5 出站过滤对齐 sub2api：一块无效 thinking 或 redacted 块拆掉整段签名历史，空轮删除。
• 没有 type 但带 thinking 字段的块也算无效。redacted_thinking 有 data 就留，否则看签名。
• 版本 1.3.183。cli-hop 首跳和默认 HTTP 保留路径不变。

Test

• anthropic-policy、cli-hop-body、mid-convo-effort：79 pass。

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Note

Medium Risk
Changes outbound message shaping for Anthropic 5.5 thinking history on the default (non-preserve) path; misclassification could strip valid chains or leave bad blocks, affecting multi-turn adaptive-thinking sessions.

Overview
Release 1.3.183 tightens outbound thinking / redacted_thinking sanitization for Opus, Sonnet, and Haiku 5.5, matching sub2api behavior documented in docs/PROTOCOL.md.

On 5.5 models, stripInvalidThinkingBlocks now treats any non-empty, non-dummy signature as valid (no 24-character cutoff). redacted_thinking is kept when it has data, otherwise when its signature passes the same rules. If history contains one invalid block—including blocks without type but with a thinking field—the gateway strips the entire signed thinking chain (all later thinking / redacted_thinking), leaves only visible text, and drops turns that end up empty. When every block is valid, nothing is chain-stripped. Older models still use per-block filtering with the 24-character signature rule; redacted_thinking without long signatures is dropped as before.

cli-hop first hop and default HTTP paths that set preserveThinkingBlocks: true are unchanged (still pad missing signature without chain teardown). Unit tests in anthropic-policy, cli-hop-body, and mid-convo-effort cover chain drops, short signatures on 5.5, and preserve-path behavior.

^{Reviewed by Cursor Bugbot for commit cdf8b37. Configure here.}