23 Lean Workbook statements with a phantom-variable (binder-escape) defect

Hello,

A static check calibrated on known-defective statements (and verified in Lean 4.9)
finds 23 Lean Workbook statements whose big-operator body is unparenthesised, so the
binder variable escapes its scope. Under autoImplicit these elaborate with a phantom
universally quantified variable and do not state the intended mathematics. An example
is a telescoping identity that parses as (sum of (k+1)!) minus a phantom k factorial.
Since the corpus is used as a training reward source, these items pay reward for
proving accidents. Full list, contexts, and the detector script attached on request.

Request the full list, contexts, and detector script mentioned in the issue, then inspect the 23 Lean Workbook statements and their big-operator bindings. Verify each statement in Lean 4.9 and confirm that the corrected corpus no longer elaborates with phantom variables or rewards proofs of unintended mathematics.

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