fix(pin_world_xy): align rotation direction and mirror axis with eeschema

Two bugs in WireDragger.pin_world_xy (and corresponding bugs in
PinLocator.get_pin_angle) caused pin coordinates and angles to land on
the wrong pin in 4 of 8 polarized cases (rot=90, rot=270, mirror x on a
vertical part, mirror y on a vertical part). Verified end-to-end against
`kicad-cli sch export netlist`.

(1) Rotation direction. After PR #145's `-ly` Y-flip, calling the
standard math (Y-up CCW) `_rotate` is effectively CW in screen Y-down.
eeschema's TRANSFORM(0,1,-1,0) for rot=90 is screen-CCW. They agreed at
0° and 180° (where the rotation matrices coincide) but disagreed at 90°
and 270°.

(2) Mirror axis semantics swapped. Per eeschema symbol.h:43-44,
SYM_MIRROR_X = TRANSFORM(1,0,0,-1) negates Y, and SYM_MIRROR_Y =
TRANSFORM(-1,0,0,1) negates X. Our code did the inverse: `mirror_x`
negated the X component and `mirror_y` negated the Y component.

Fix shape for `_rotate`: chose option (b) — leave `_rotate` as standard
math and negate the angle at the call site (`_rotate(lx, ly, -rotation)`).
This converts math-CCW to screen-CCW without disturbing
`TestRotatePoint`'s direct expectations of `_rotate`.

Final composition order in `pin_world_xy` matches eeschema's parser
(rotation set first into m_transform, then mirror composed via
`new = old * temp` so the mirror is applied first to the coordinate):
  1. Y-flip:    ly = -ly                    (lib Y-up → screen Y-down)
  2. Mirror:    if mirror_x: ly = -ly       (negate screen-Y)
                if mirror_y: lx = -lx       (negate screen-X)
  3. Rotate:    _rotate(lx, ly, -rotation)  (screen-CCW)
  4. Translate: add (sym_x, sym_y)

Verified by hand for {rot=90, rot=270} × {none, mirror_x, mirror_y}
against the TRANSFORM matrices in transform.cpp:44 and symbol.h:43-44.

`PinLocator.get_pin_angle` mirrors the same composition in angle space.
For an angle, Y-flip and mirror_x both negate the angle; mirror_y maps
to (180 - angle). The screen-CCW rotation in `pin_world_xy` corresponds
to subtracting (not adding) the symbol rotation in standard atan2
convention — fixed accordingly. Geometry test
(`test_get_pin_angle.py::test_get_pin_angle_matches_geometric_expectation`)
derives expected angles from `pin_world_xy` itself, so it pins the two
together.

`tests/test_rotate_schematic_mirror.py::test_pin_positions_mirror_x_flips_x`
encoded the OLD inverted semantics and is updated/renamed to
`test_pin_positions_mirror_x_flips_y` with a pin that has non-zero Y so
the assertion is meaningful under the corrected semantics.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tests/test_rotate_schematic_mirror.py

@@ -163,19 +163,21 @@ def test_pin_positions_unchanged_at_same_transform():
         assert old_xy == new_xy
 
 
-def test_pin_positions_mirror_x_flips_x():
-    """mirror_x should negate the local X coordinate before rotation."""
+def test_pin_positions_mirror_x_flips_y():
+    """mirror_x = SYM_MIRROR_X = TRANSFORM(1,0,0,-1) negates the screen-Y
+    coordinate (eeschema symbol.h:43-44), not X. With the lib→screen Y-flip
+    applied first, this means the pin's screen Y is reflected back to lib Y."""
     sch = _make_sch()  # at (75, 105, 0), no mirror
 
-    fake_pins = {"1": {"x": 2.0, "y": 0.0}}
+    fake_pins = {"1": {"x": 0.0, "y": 2.0}}
     with patch.object(WireDragger, "get_pin_defs", return_value=fake_pins):
         pos = WireDragger.compute_pin_positions_for_rotation(sch, "Q1", 0.0, True, False)
 
     _, (old_xy, new_xy) = next(iter(pos.items()))
-    # old: pin at local (2, 0), world = (75+2, 105) = (77, 105)
-    assert abs(old_xy[0] - 77.0) < 1e-4
-    # new: mirror_x → local (-2, 0), world = (75-2, 105) = (73, 105)
-    assert abs(new_xy[0] - 73.0) < 1e-4
+    # old: pin at lib (0, 2). Y-flip → (0, -2). No mirror. World = (75, 105-2) = (75, 103).
+    assert abs(old_xy[1] - 103.0) < 1e-4
+    # new: mirror_x → negate screen-Y → (0, 2). World = (75, 105+2) = (75, 107).
+    assert abs(new_xy[1] - 107.0) < 1e-4
 
 
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