Resolve outstanding TODO/FIXME comments in source

[nbassler]

Background

Several TODO/FIXME comments were identified during the modernization effort
(branch 64-modernize-repository) but left unresolved as they touch library
internals and are out of scope for a pure tooling/infrastructure change.

Items

Possible memory leak — dedx.c (dedx_allocate_workspace)

A TODO comment flags a potential memory leak in dedx_allocate_workspace.
This was also independently confirmed by clang-analyzer-unix.Malloc during
the clang-tidy audit (see clang-tidy tracking issue).

Broken path check — dedx_file_access.c

A FIXME comment indicates a path validation check that does not work as intended.
Related to the global mutable folder variable (see separate issue).

Naming ambiguity — dedx_tools.c

ion_a vs ion_A — inconsistent capitalisation for the ion mass number variable.
Should be resolved together with the broader _prefixed identifier cleanup
flagged by bugprone-reserved-identifier in the clang-tidy audit.

Related issues

• clang-tidy tracking issue (stream leaks, malloc leaks, dead stores)
• Global folder variable refactor