Batch 242-A ACCEPTED -- the (8.4.25) cross contraction is DISCHARGED (protocol (b)): it is the grounded l = 0 face of Theorem 8.8.9, registered in a new file

Eliminated one open input and registered one sharper one, per the batch protocol.

* ELIMINATED: MM.FLM810T861S.crossContraction_evenCocycle is no longer a `sorry`.  It is now a
  theorem, derived from the grounded l = 0 face through the landed batch-223-B equivalence
  MM.FLM86M8625P.modeFieldCommInsertionStep8625_iff_spanningEventual and the new
  MM.FLM810CCG.corollary851SpanningEventualWindows_of_groundedZeroFace.
* REGISTERED (new file Definitions/MMFLM810CrossContractionFromGrounded.lean, MM.FLM810CCG):
  MM.FLM810CCG.groundedZeroFace_evenCocycle : MM.FLM810ASM.GroundedZeroFace (ZAligned E) -- the
  grounded l = 0 face at the honest field (one window carrying the identity at every monomial, plus
  the iterate's vanishing above it).  Guarded: [propext, sorryAx, Classical.choice, Quot.sound].
* Correction of record (NOTES section 141): the bare `exists N` reading of the l = 0 slice of
  FacesAtStates does NOT imply the display -- at N = 0 both sides of the identity are the empty sums
  (vacuous), while the grounded form has no such corner (at K = 0 it asserts commutatorFamily = 0).
  So the l = 0 face must be read grounded.  MM.FLM810CCG.corollary851SpanningEventualWindows_of_groundedZeroFace
  proves the implication; MM.FLM810CCG.crossIterate_zero_eq_of_component_eventually_zero is the
  window step.
* The two open inputs are now MM.FLM810CCG.groundedZeroFace_evenCocycle (the display, grounded) and
  MM.FLM88T889S.theorem889_faithful (FacesAtStates) -- still the same section 8.6 engine.
* Naming: at the owner's instruction the Lean sources now read mathematically (no campaign terms like
  "hole"); the new module is MMFLM810CrossContractionFromGrounded.lean and the touched files' prose
  was swept accordingly.

Build: the new module, the 8.6.1 file and the 8.10.2 file all --- OK ---; FinalCheck.lean GREEN;
HANDOVER.md section 1.1 records the elimination and the sharpened entry.
