Add assumptions to default symbols
Issue
The formula for tilt stability central charge needs to be written more directly, which involves applying "real part" and "imaginary part" functions. But all symbols are assumed to be generic complex numbers by default.
Parameters for the stability conditions.
Default to rational, but allow customization to reals too.
Parameters for chern characters
Functions generating "generic" Chern characters with symbols need to have appropriate assumptions (rational or integer).