length of free_resolution gives wrong results

**Describe the bug** It seems that `length` has problems with short free resolutions of graded modules. This bug has been discovered when confronting over R=QQ[x] the free resolution of - R itself, which is 0 -> R; - R/(x), which is 0 -> R -> R; Obviously, the second resolution is longer. **To Reproduce** ``` using Oscar # QQ[x] M1 = free_module(R,1) length(free_resolution(M1)) # QQ[x]/(x) M2 = cokernel(matrix(R, [x])) length(free_resolution(M2)) ``` The function `length` returns `1` for both free resolutions. **Expected behavior** The expectation is that `length` returns the number of non-zero terms in the free resolution, so `1` for the free resolution of `M1` and `2` for the one of `M2`. This information can be obtained, for example, by the following code (supposing that `rank` is a cheap function for terms of `FreeResolution`): ``` function length_complex(F::FreeResolution) l=0 while rank(F[l])>0 l=l+1 end return l end ``` **System:** ``` julia> Oscar.versioninfo(full=true) OSCAR version 1.7.0 combining: AbstractAlgebra.jl v0.47.6 GAP.jl v0.16.2 Hecke.jl v0.39.3 Nemo.jl v0.52.4 Polymake.jl v0.13.7 Singular.jl v0.28.2 building on: FLINT_jll v301.300.102+0 GAP_jll v400.1500.100+1 GAP_lib_jll v400.1500.100+0 Singular_jll v404.101.502+0 libpolymake_julia_jll v0.14.3+1 libsingular_julia_jll v0.47.9+0 polymake_jll v400.1500.0+0 polymake_oscarnumber_jll v0.3.12+1 See `]st -m` for a full list of dependencies. Julia Version 1.12.5 Commit 5fe89b8ddc1 (2026-02-09 16:05 UTC) Build Info: Official https://julialang.org release Platform Info: OS: Linux (x86_64-linux-gnu) CPU: 12 × AMD Ryzen 5 8500GE w/ Radeon 740M Graphics WORD_SIZE: 64 LLVM: libLLVM-18.1.7 (ORCJIT, znver4) GC: Built with stock GC Threads: 1 default, 1 interactive, 1 GC (on 12 virtual cores) Official https://julialang.org release ```