Incorrect bond type written for aromatic bonds in MDL SDF files

Environment Information

Open Babel version: 3.1.0
Operating system and version: MacOS 26.4.1

Expected Behavior

Aromatic bonds should be written with bond type 4, as defined by the CTF format specification.
https://www.daylight.com/meetings/mug05/Kappler/ctfile.pdf

Actual Behavior

Aromatic bonds are written with bond type 5.

Steps to Reproduce

If we try to convert valid .hin file with explicit aromatic bonds

obabel -ihin test.hin -osdf

We get incorrect .sdf file with bond types 5 instead of 4

test.hin:

mol 1 ""
atom 1 - C   **  -  0.00041 -2.02520   0.08170  -1.43130 4 2 s 16 s 17 s 18 s 
atom 2 - N   **  - -0.31305 -0.59160   0.03810  -1.25400 3 1 s 3 s 19 s 
atom 3 - C   **  -  0.26580  0.00000   0.00000   0.00000 3 2 s 4 d 5 s
atom 4 - O   **  - -0.26841 -0.63540   0.00000   1.05240 1 3 d
atom 5 - C   **  -  0.16730  1.45700   0.00000  -0.00000 3 3 s 6 a 14 a
atom 6 - N   **  - -0.24466  2.06180  -0.00000  -1.21050 2 5 a 7 a
atom 7 - C   **  -  0.05459  3.42170  -0.00630  -1.27630 3 6 a 8 a 20 s
atom 8 - C   **  -  0.09253  4.24880  -0.00120  -0.15090 3 7 a 9 a 13 a
atom 9 - N   **  - -0.25334  5.59930   0.01840  -0.23730 2 8 a 10 a
atom 10 - C   **  -  0.02833  6.32380   0.02090   0.90390 3 9 a 11 a 21 s
atom 11 - C   **  - -0.04288  5.77150   0.00830   2.16650 3 10 a 12 a 22 s
atom 12 - C   **  - -0.04751  4.38780  -0.00460   2.25710 3 11 a 13 a 23 s
atom 13 - C   **  -  0.04556  3.60070  -0.00600   1.09670 3 8 a 12 a 14 a
atom 14 - C   **  -  0.15640  2.20180  -0.00900   1.17270 3 5 a 13 a 15 s
atom 15 - O   **  - -0.50383  1.58450  -0.02990   2.40220 2 14 s 24 s
atom 16 - H   **  -  0.04260 -2.52270  -0.51060  -0.65900 1 1 s
atom 17 - H   **  -  0.04260 -2.26580  -0.31450  -2.42050 1 1 s
atom 18 - H   **  -  0.04260 -2.35050   1.12280  -1.36040 1 1 s
atom 19 - H   **  -  0.14873 -0.02080   0.10830  -2.08910 1 2 s
atom 20 - H   **  -  0.08515  3.83270  -0.00470  -2.28050 1 7 s
atom 21 - H   **  -  0.08296  7.39990   0.03380   0.76630 1 10 s
atom 22 - H   **  -  0.06328  6.39260   0.01080   3.05410 1 11 s
atom 23 - H   **  -  0.06257  3.92510  -0.01060   3.24160 1 12 s
atom 24 - H   **  -  0.29226  2.25830  -0.03340   3.10160 1 15 s
endmol 1

output:

test.hin
 OpenBabel07242613313D

 24 25  0  0  1  0  0  0  0  0999 V2000
   -2.0252    0.0817   -1.4313 C   0  0  0  0  0  0  0  0  0  0  0  0
   -0.5916    0.0381   -1.2540 N   0  0  0  0  0  0  0  0  0  0  0  0
    0.0000    0.0000    0.0000 C   0  0  0  0  0  0  0  0  0  0  0  0
   -0.6354    0.0000    1.0524 O   0  0  0  0  0  0  0  0  0  0  0  0
    1.4570    0.0000   -0.0000 C   0  0  2  0  0  0  0  0  0  0  0  0
    2.0618   -0.0000   -1.2105 N   0  0  0  0  0  0  0  0  0  0  0  0
    3.4217   -0.0063   -1.2763 C   0  0  0  0  0  0  0  0  0  0  0  0
    4.2488   -0.0012   -0.1509 C   0  0  1  0  0  0  0  0  0  0  0  0
    5.5993    0.0184   -0.2373 N   0  0  0  0  0  0  0  0  0  0  0  0
    6.3238    0.0209    0.9039 C   0  0  0  0  0  0  0  0  0  0  0  0
    5.7715    0.0083    2.1665 C   0  0  0  0  0  0  0  0  0  0  0  0
    4.3878   -0.0046    2.2571 C   0  0  0  0  0  0  0  0  0  0  0  0
    3.6007   -0.0060    1.0967 C   0  0  1  0  0  0  0  0  0  0  0  0
    2.2018   -0.0090    1.1727 C   0  0  2  0  0  0  0  0  0  0  0  0
    1.5845   -0.0299    2.4022 O   0  0  0  0  0  0  0  0  0  0  0  0
   -2.5227   -0.5106   -0.6590 H   0  0  0  0  0  0  0  0  0  0  0  0
   -2.2658   -0.3145   -2.4205 H   0  0  0  0  0  0  0  0  0  0  0  0
   -2.3505    1.1228   -1.3604 H   0  0  0  0  0  0  0  0  0  0  0  0
   -0.0208    0.1083   -2.0891 H   0  0  0  0  0  0  0  0  0  0  0  0
    3.8327   -0.0047   -2.2805 H   0  0  0  0  0  0  0  0  0  0  0  0
    7.3999    0.0338    0.7663 H   0  0  0  0  0  0  0  0  0  0  0  0
    6.3926    0.0108    3.0541 H   0  0  0  0  0  0  0  0  0  0  0  0
    3.9251   -0.0106    3.2416 H   0  0  0  0  0  0  0  0  0  0  0  0
    2.2583   -0.0334    3.1016 H   0  0  0  0  0  0  0  0  0  0  0  0
  1  2  1  0  0  0  0
  1 16  1  0  0  0  0
  1 17  1  0  0  0  0
  1 18  1  0  0  0  0
  2  3  1  0  0  0  0
  2 19  1  0  0  0  0
  3  4  2  0  0  0  0
  5  3  1  6  0  0  0
  5  6  5  0  0  0  0
  5 14  5  0  0  0  0
  6  7  5  0  0  0  0
  7 20  1  0  0  0  0
  8  7  5  6  0  0  0
  8  9  5  0  0  0  0
  8 13  5  0  0  0  0
  9 10  5  0  0  0  0
 10 11  5  0  0  0  0
 10 21  1  0  0  0  0
 11 12  5  0  0  0  0
 11 22  1  0  0  0  0
 12 23  1  0  0  0  0
 13 12  5  1  0  0  0
 13 14  5  0  0  0  0
 14 15  1  6  0  0  0
 15 24  1  0  0  0  0
M  END
$$$$

Start by running obabel -ihin test.hin -osdf with the issue's test.hin input and compare the aromatic bond records in the generated SDF with the cited CTfile specification. Trace the SDF output path from this conversion and verify that aromatic bonds are emitted with bond type 4 rather than 5; done means the reproduced output and a regression check show the corrected type.