Fix grader import path: use root-level graders module instead of server.graders

Add score:0.5 to all YAML tasks, make graders callable without args, fix health status

Bypass cached validator endpoints

chore: force HF rebuild with deploy canary v3

chore: add build label to force HF Space Docker rebuild

simplify openenv.yaml: pure ASCII, remove all non-essential sections, copy yaml to WORKDIR in Docker

fix: use server.graders:... paths to match platform example format exactly

fix: resolve all 3 pre-submission critical risks

chore: pre-iteration-1 snapshot — 75/75 e2e passing, baseline bug fixed

Initial Commit