Serialize aware reverse-fill boundaries as `YYYYMMDD-HH:MM:SS`
before handing them to `ib_async`.
This avoids Gateway error 10314 from its trailing-`UTC` format and
drops the unfinished EST comparison breakpoint from `Client.bars()`.
Prompt-IO: ai/prompt-io/opencode/20260729T034106Z_922a5df8_prompt_io.md
(this patch was generated in some part by `opencode` using `gpt-5.6-sol` (`openai`))
