MacProj::mac_sync_compute (known-edge-state overload) and OutFlowBC::SemiGrow/SemiCoarsen have no callers #239

Location: Source/MacProj.H:72-80, Source/MacProj.cpp:749-802, Source/OutFlowBC.H:16-22, Source/OutFlowBC.cpp:9-27
Severity: Low — dead code
Category: Docs
Based on commit bb697bf5 (line numbers refer to that tree).

Problem

The second mac_sync_compute overload, which takes precomputed edge states for a single
scalar, is not called anywhere in Source/, Exec/ or Tutorials/; the only call is
the full-state overload from NavierStokes::mac_sync (Source/NavierStokes.cpp:1486).
Its header comment still describes a use case from another code ("div rho U h ...").
#204 kept it compiling by aliasing Sync as the state MultiFab handed to ComputeAofs:

// Source/MacProj.cpp:787-794
    MultiFab Smf(Sync, amrex::make_alias, Sync_indx, ncomp);
    ...
    ns_level.ComputeAofs(Sync, /*Ssync_comp*/ Sync_indx, state_comp,
                         ncomp,
                         /*State*/ Smf, /*S_comp*/ 0,           //not used when known_edgestates

so the function now exists only to be maintained. Likewise OutFlowBC::SemiGrow and
OutFlowBC::SemiCoarsen (Source/OutFlowBC.cpp:9-27) are unreferenced; the only
OutFlowBC members in use are GetOutFlowFaces and HasOutFlowBC.

Impact

None at run time. The unused overload is a maintenance trap: it does not add Ucorr to
mac_reg the way the live overload does (Source/MacProj.cpp:723-738), so a future
caller would silently get an inconsistent MAC register.

Suggested fix

Remove the overload (Source/MacProj.H:72-80, Source/MacProj.cpp:741-802) and
SemiGrow/SemiCoarsen (Source/OutFlowBC.H:16-22, Source/OutFlowBC.cpp:9-27).
Plain deletions; no diff given.