keep cleaning source_cell

[mohanchen]

keep cleaning source_cell

[Critsium-xy]

Two Doxygen-specific issues in the new comments that will affect the generated docs:

1. ///< used as a section header documents the wrong thing (and drops the text)

///< is a trailing comment — it documents the preceding declaration, not the line below it. In several places it's placed on its own line before a member as a section marker, e.g. in read_pp.h / pseudo.h:

///<PP_HEADER>
bool has_so = false;   ///< if .true. includes spin-orbit

Two problems here:

• The ///<PP_HEADER> attaches backward (to whatever came before), so it does not label has_so.
• Doxygen parses <PP_HEADER> as an unknown HTML tag and silently drops it (with a warning), so the section text is lost entirely.

Same pattern appears with ///<PP_INFO>, ///<PP_MESH>, ///<Dynamic arrays>, ///<VWR format>, ///<USPP>, ///<UPF201 format> (read_pp.h), and ///<K-point information> (parallel_kpoints.h).

Suggested fix — use a member group instead:

/// @name PP_HEADER
/// @{
bool has_so = false;   ///< if .true. includes spin-orbit
int  nv     = 0;       ///< UPF file version number
/// @}

or, if a group is overkill, just a plain /// line (no <, and avoid the angle brackets so it isn't read as HTML):

/// PP_HEADER
bool has_so = false;   ///< ...

2. Comma-listed @param won't render correctly

In symmetry.h (rhog_symmetry):

* @param nx, ny, nz grid dimensions
* @param fftnx, fftny, fftnz FFT grid dimensions

@param expects a single identifier; Doxygen will warn about undocumented params and mis-render these. Please split them:

* @param nx  grid dimension in x
* @param ny  grid dimension in y
* @param nz  grid dimension in z

(or use @param nx,ny,nz with no space after the commas, which Doxygen does accept as a shared description).