Source-citation existence verifier for S185 generator theses

Add validate.assertCitationsResolveInCorpus(thesis, generationSources) to forecaster/validate.js: takes a generated thesis and its declared generation_sources, then for each cited source URL/identifier in the thesis body, checks (a) it exists in the corpus_access index of generation_sources, and (b) the thesis-body terms have a minimum 30% bigram overlap with the source's text within a 500-char window. Theses failing either check are dropped pre-lock (not silently — write to forecaster/data/rejected_theses.log with reason). Wire into generator.js between batch emission and the candidates-passed-to-precommit handoff. Pure deterministic; no new LLM cost.

Some fraction of S185 theses currently 'cite' sources by URL/handle without the source meaningfully supporting the claim (LLM citation hallucination is a known failure mode even on tuned-up generators). Expected: 5-25% of theses rejected on first run; after generator prompt tightening, rate drops to <5%. The first locked batch (fwd_2026-06-08_h45) can be retro-checked.

Run on the fwd_2026-06-08_h45 batch (12 theses, all currently locked). If zero theses fail the existence check AND zero fail the overlap check, the verifier is too lax (or the generator is already perfectly source-grounded — possible but would be a strong positive result). If it rejects >50% of theses, the overlap threshold is miscalibrated.

Rejected at the council verdict. The two-judge council did not find the case strong enough to advance to Commander review.