discovery:research outcome gate never asks whether a claim follows from its sources #4452

Problem

/discovery:research's outcome gate grades where each accepted claim's sources came from (tier,
recency, independence, confidence) but has no criterion asking whether the claim follows from those
sources. A live five-topic fan-out passed both parent-side gates and five quote-fidelity verifiers,
and three fresh-context inference auditors then found sixteen inference failures behind verbatim
quotes: a reversed disconfirmation, a primary whose headline result runs against the claim, a source
applied to a variable it never measured, and seven cases where a qualifier recorded in a slice was
dropped where the synthesis used the claim.

The standing verifier criterion ("independent corroboration and HIGH confidence per accepted claim")
reads as re-fetch-and-confirm-quotes, so no verifier asks the inference question.

Ask

• Add a verifier-owned outcome-gate row for joint-inference validity per accepted claim, with the
  variable, population, and hedge-survival sub-tests.
• Carry what a verifier needs to grade it in the sidecar header schema.
• Brief the parent's sibling verifier on every verifier-owned row, and verify a fan-out's synthesized
  root index for hedge survival.
• Pin it in the plugin's contract test.