chore: prepare Build Small submission

docs: update README, demo script and social post for OCR and new UI

docs: clean up placeholders and uncertainties; align Gradio version with HF Space

fix: remove invalid sdk_version from Space YAML config

docs: fill README placeholders with STEM user, example feedback, and HF username

chore: switch default model to MiniCPM5-1B and update README for STEM user

docs: add HF Space deployment instructions

feat: Gradio Space with NL->LaTeX, validation, auto-fix and render

init: Backyard AI Space scaffold