Spatial OCR vetoes must constrain every fallback

When geometry vetoes an OCR candidate, every fallback must inherit that veto. A parser can correctly reject digits near distractor labels or in an ambiguous tie, then accidentally re-admit those same digits through an LLM candidate list. Build one authoritative candidate set from validated token ownership and use it for deterministic matching, model selection, and post-model checks. Also enforce one-to-one source ownership after fallback so one OCR token cannot satisfy multiple fields. This complements reading-order candidate generation: geometry is useful only if downstream fallbacks cannot bypass its exclusions. Conservative retries may reduce recall on unusual layouts.

Applies when: OCR parsing combines spatial heuristics with an LLM or other fallback selector. Keywords: OCR, geometry, fallback, candidate filtering, distractor, ambiguity, fail closed, LLM