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Merge pull request #5 from francisco-magana/hygienepile-0k/nah-9-1b-fallback-ready-as-a-config-flip-bring-to-day-1-400-sync

Merge pull request #3 from francisco-magana/hygienepile-0k/nah-8-grade_answer-strict-json-grading-parserrepair-retry

[NAH-9] Make the smaller-model fallback a one-env-var config flip

[NAH-8] grade_answer: strict-JSON grading + parser/repair retry

[NAH-16] Commit content_pipeline.py stubs

Add app, content pipeline, learning engine, and gitignore