6fac4ffa

By: Valentin Hirschi <valentin.hirschi@gmail.com>

Add native LTD representations and stability rescue

Generate CFF and LTD with ordered representation selection, complete LTD
residue sums, local 4D UV composition, and per-attempt stability dispatch.
Cover physical cuts and threshold counterterms, persistence and standalone
evaluation, CLI diagnostics, scalar benchmarks, and overlap-center objectives.

Use stock SymJIT 2.26.3 and validate the full scalar matrix and CI suite.