Two cosmetic bugs fixed:
1. JSON inside code fences was being filtered - now tracks fence state
and passes through all content inside ``` ... ``` blocks
2. Indented JSON was being filtered - now recognizes that real tool
calls are never indented, so indented JSON is always documentation
Changes:
- Added in_code_fence and fence_buffer fields to FilterState
- Added track_code_fence() to detect ``` markers (with/without language)
- Added pass_through_char() for content inside code fences
- Modified '{' handling to only filter when no leading whitespace
- Added 4 new unit tests for code fence and indentation cases
- Updated 3 stress tests to expect new (correct) behavior
All 16 filter_json unit tests and 59 stress tests pass.
6ff21a7d47