- New context_compressor.go: pure functions operating on raw JSON body
(gjson/sjson pattern). approxTokens uses chars/4 heuristic.
- compressMessages: removes oldest messages from front, treating
consecutive assistant(tool_use)+user(tool_result) pairs as atomic units
to prevent orphaned tool_result blocks.
- Hooked into Forward() after StripEmptyTextBlocks, gated on
account.Credentials[enable_context_compression].
- Config: gateway.context_compression.max_tokens (default 190000).
- 8 unit tests covering: approx tokens, no-op when under budget,
oldest-message trimming, tool pair preservation, atomic pair removal,
body passthrough, body trimming.
