1. add_schematic_net_label failed on schematics with no existing labels.
The clone-based path required a pre-existing label to copy from;
the documented "fallback to sexpdata" was a misleading log line —
the RuntimeError was caught and the call silently returned False.
Restore hand-built sexpdata construction (without the buggy
fields_autoplaced token, with orientation-aware justify).
2. get_pin_angle returned the wrong angle for every mirrored symbol
(off by exactly 180°, all rotations, both mirror axes). The
mirror_x and mirror_y formulas were swapped relative to the
pin_world_xy convention — pin_world_xy mirrors a position by
flipping its local axis component, so the matching angle
transform is (180 - θ) for mirror_x and -θ for mirror_y.
Add regression tests:
- test_add_label_empty_schematic.py — first label on empty schematic,
orientation-aware justify.
- test_get_pin_angle.py — full 24-case matrix
(4 rotations × 3 mirror states × 2 pins).
