Extension height grows incorrectly with finger width

[fanoplane]

The line referenced below should likely be modified to:

d_m1_yb = od_yc - m1_h//2

One of the requirements for top/bottom extension height is to maintain proper line-end spacing for m1. As written in the existing code, ExtInfo d_m1_y claims d_m1_yt extends roughly m1_h//2 beyond od_yt (assuming m1_h is close to od_h), even though the drain m1 is not actually drawn this way based on get_laygo_conn_yloc_info(). Without suggested modification, for fingers with large w, d_m1_yt causes the extension to grow, roughly proportional to the increase in w, when it should not.

BAG2_TEMPLATES_EC/abs_templates_ec/laygo/planar.py

Line 941 in ed6bd51

d_m1_yb = od_yc