Adds cli_dispatch.{hpp,cpp} containing a static table of every
extracted handler family's dispatch function. The table-walker
tryDispatchAll() iterates the table once per argv token, calling
each handler in turn. handleConvertSingle stays as a special-
case call in main.cpp because it threads dataPath through.
main.cpp shrinks from 486 to 236 lines (-250). Adding a new
handler module now requires touching only cli_dispatch.cpp's
include list + table — no main.cpp edits, no growing
if-else chain. The 60+ #include lines for individual cli_*
modules collapse to one #include for cli_dispatch.hpp.
