Admit identity-seeded reduction controls with total publication

[PraneethMerugu]

Summary

• recognize an identity-seeded reduction as a total field publication for a
  later field-derived control
• retain total-publication admission for total Unique laws and reject
  existing-value-seeded reductions
• require the producing stage itself to be ungated while permitting prefix,
  mask, and subset controls that still initialize every destination
• exercise stale-gate reset, empty and active reductions, total unique
  publication, prefix/mask/subset selection, and relaxed atomic reduction
• document the total-producer dependency rule and expose the shared CPU/Metal
  fixture through the ordinary inventories

Why this is required

CorePotts' bounded maintained-minimum reconstruction computes whether the
completed structural transaction changed any ownership or source value, then
uses that reduced Boolean field to gate the sole full-lattice rebuild. A
reduction with an IdentitySeed initializes every destination even when no
contribution is routed, but LocalMath's dependency planner previously assumed
that every total publication law owned a coverage field. Reduce
deliberately does not. This change gives the existing planner one semantic
totality predicate; it adds no executor, registry, or alternate scheduling
path.

Validation

• focused reduction-control, planning, reduction, package-quality, and
  inventory cohort: 122/122
• focused actual-Metal control fixture with bounds checking and scalar indexing
  disabled: 62/62
• full ordinary LocalMath CPU suite: 1,797/1,797
• complete ordinary LocalMath Metal inventory: 483/483
• strict documentation build: passed
• independent review: no blocking finding
• downstream CorePotts maintained-minimum cold construction passed the
  previously failing reduction-gate planning boundary; subsequent execution
  exposed a separate Sequential transaction-alias defect in the Core
  candidate

CPU and Metal are the qualified execution paths. This does not claim total
publication for a stage controlled by a gate, for an ExistingSeed
reduction, or for untested CUDA, ROCm, custom backends, or provider array
wrappers.