fix: load real DCLM bundle format in CORE-22 loader

[bitzic]

• schema parser reads {context_options, continuation, gold}, broadcasting the shared continuation across options (winograd-schema scoring)
• lm parser reads the continuation key (bundle uses it, not target)
• both keep legacy {contexts,continuations}/{context,target} for fixtures
• add task->file aliases: winograd->winograd_wsc, hellaswag_zeroshot->
  hellaswag, jeopardy->jeopardy_all
• before: 2 schema + 9 lm tasks crashed the parser + 3 failed file resolution -> downstream eval was effectively mc-only (11/22)
• now all 22 CORE-22 tasks load from the real bundle
• tests: real-format schema/lm rows, alias resolution, skip-if-absent real-bundle smoke (loads all 22)