LLM providers like MiniMax wrap JSON responses in markdown code fences
(```json ... ```), causing JSON parse failures and 5-11 retries per
extraction. The existing fence stripping logic was gated to only
"lmstudio" and "ollama" providers (and for Ollama, unreachable due to
the _call_ollama_native redirect).
Changes:
- Extract _strip_code_fences() helper function
- Apply fence stripping to all providers in call() (not just local)
- Add fence stripping safety net to _call_ollama_native()
- Add 10 tests covering bare JSON, fenced JSON, malformed fences,
and real-world MiniMax response format
Fixesvectorize-io/hindsight#645
Co-authored-by: feniix <feniix@desktop>
