Summary

• cherry-pick the core Feishu fenced-code-block row-splitting fix from fix(feishu): split fenced code blocks in post payload #8638 by @sgaofen with authorship preserved
• harden fence handling so fence-like lines inside a code block are not misparsed as closing fences
• preserve trailing spaces inside fenced code blocks and add regression coverage for both edge cases

Why

Feishu post/md rendering can swallow trailing content when a fenced code block is embedded in one large markdown element. Splitting fenced blocks into their own post rows preserves normal markdown while keeping the code block visible.

This salvage keeps the original contributor change, then adds a small follow-up commit to address parser edge cases found during review.

Original PR

• Based on fix(feishu): split fenced code blocks in post payload #8638 by @sgaofen

Follow-up fixes in this salvage

• use real fence-line detection instead of treating any line starting with ``` as a fence
• preserve trailing spaces inside fenced code blocks
• add regression tests for fence-like code lines and trailing-space preservation

Test plan

• python3 -m py_compile gateway/platforms/feishu.py tests/gateway/test_feishu.py
• source /Users/kshitij/.hermes/hermes-agent/venv/bin/activate && /Users/kshitij/.hermes/hermes-agent/scripts/run_tests.sh tests/gateway/test_feishu.py -q
• direct payload smoke check for a fence-like code line inside a fenced block

Attribution note

• prerequisite contributor mapping PR: chore: add sgaofen to AUTHOR_MAP #12506