Corrected companion statement: companions over finite extensions of E_lambda

Second independent review found the previous main theorem stronger than
Lafforgue's theorem in two ways, both filed as limitations: the conclusion
placed companions over E_lambda itself, and IsIrred weakened the hypothesis
from absolute irreducibility to E_lambda-irreducibility.

- exists_companion replaces exists_isCompatibleFamily_of_irreducible; stated
  pointwise in lambda, with the companion over a bundled finite extension M/E_lambda
  carrying the module topology (IsModuleTopology).
- A is now a finite-type Fq-algebra with a scalar tower to K, so Spec A is a
  smooth affine curve; without this the statement was satisfiable by an
  everywhere-unramified companion-matrix construction.
- SpanFull: absolute irreducibility via Burnside, with no algebraic closure.
- P is data, so the same polynomials tie companion to rho_0; drops rho lam0 = rho0.
- Fixed a docstring that reasserted the false well-definedness claim and cited
  the deleted axiom IsFrobeniusSystem.isConj_of.
- Removed empty namespace blocks; named the two supplied instances.

Author: SuvirRathore