Hybrid momentum references nonexistent MOL face arrays

Location: Source/hydro/Castro_mol_hydro.cpp:623-645.

Finding

The HYBRID_MOMENTUM block reads qx_arr and qy_arr in its radial pressure
gradient. Neither identifier is declared in construct_mol_hydro_source. The
actual face-state data are stored in the direction-indexed qe FArrayBoxes.

This independently blocks true-SDC builds with USE_HYBRID_MOMENTUM=TRUE. That
feature requires DIM=3, so the dimension-guard failure in report 01 is also
present, but correcting that brace alone will not fix these undeclared arrays.

Evidence

Compiled the unchanged MOL object with DIM=3 USE_MPI=FALSE USE_TRUE_SDC=TRUE USE_HYBRID_MOMENTUM=TRUE. GCC explicitly reports qx_arr undeclared at line
641 and qy_arr undeclared at line 642, in addition to the independent
brace-related errors. Build instructions are in README.md.

Proposed fix

Before the hybrid kernel, define const array views from qe[0] and qe[1] and
capture those views in the lambda. Use them for the existing GDPRES differences.
Address report 01 in the same build-validation pass. Audit the hybrid source for
consistency with do_hydro=0 separately before claiming that configuration is
supported.

Validation after fixing

Compile the MOL object and a full three-dimensional true-SDC executable with
hybrid momentum enabled. Run a Cartesian advection or rotating-flow case and
check that the hybrid and linear momenta stay consistent. Exercise both SDC2 and
SDC4 face-state paths.

Start at Source/hydro/Castro_mol_hydro.cpp:623-645 and read the surrounding HYBRID_MOMENTUM kernel and qe face-state setup. Review README.md build instructions, then compile the MOL object with DIM=3, USE_TRUE_SDC=TRUE, and USE_HYBRID_MOMENTUM=TRUE while addressing report 01. Done means the builds succeed and Cartesian advection or rotating-flow validation covers SDC2 and SDC4 face-state paths.