Accept span deletions in structured responses

docs/internal/prompts.md

@@ -22,6 +22,11 @@ Validator prompts receive the correction payload and description block.
 The prompt assets retain the prior task instructions and output-schema
 association. The role-bound runtime will supply the complete JSON Schema output contract
 and repair count; the definition does not own an operator-facing repair default.
+The correction-set schema requires a string replacement and accepts an empty
+string. Proposal guidance uses it for eligible span deletion and permits literal
+spacing edits; validator guidance evaluates the full before/after segment under
+each validator's existing remit. A blank resulting segment remains a domain
+rejection, not a structural schema error.
 
 `internal/framework/responseschema` remains the only embedded source for
 `correction_set.v1.json` and `validator_decision_set.v1.json`. It exposes that