Fix explain_unresolved() not excluding toleranced bearings like solve_location() does

Latent inconsistency flagged during the ocr.py refactor: solve_location()
already excludes a compass-word bearing (bearing_tolerance_deg set) from
its own bearings list before triangulating, since a toleranced bearing
names a sector, not a precise ray, and shouldn't be treated as if it
were one. explain_unresolved()'s bearings list didn't have the same
exclusion, so a toleranced-only bearing plus a distance clue could get
described as inconsistent geometry ('the bearing from X never crosses
the Ykm circle...') when the real reason nothing resolved is just that
the bearing was never usable for that math in the first place. Locked
in with a new test.

tests/test_solver.py

@@ -76,6 +76,23 @@ def test_toleranced_bearing_is_never_used_to_triangulate():
     assert not target.location.potential_coords
 
 
+def test_explain_unresolved_ignores_a_toleranced_bearing_too():
+    """A real inconsistency: solve_location() already excluded a
+    toleranced bearing from triangulation, but explain_unresolved()'s
+    own bearings list didn't, so it could describe a toleranced-only
+    bearing as if it were usable geometry. Only a distance clue is left
+    once the toleranced bearing is (correctly) excluded, one clue alone
+    is never inconsistent with itself, so there's nothing to explain."""
+    board = _board_with_spotters(Coord("J", 5, 0, 0), Coord("L", 4, 3, 0))
+    target = board.add_target(TargetType.HOSTILE_TANK, id_="1")
+    target.location = Location.from_desc("x", [
+        Clue(reference="Spotter#1", distance_km=3.0),
+        Clue(reference="Spotter#2", bearing_deg=270.0, bearing_tolerance_deg=11.25),
+    ])
+    solver.resolve_board(board)
+    assert solver.explain_unresolved(target.location, board) is None
+
+
 def test_manual_coord_override_clears_a_stale_note():
     board = _board_with_spotters(Coord("J", 5, 0, 0), Coord("J", 5, 1, 0))
     target = board.add_target(TargetType.HOSTILE_TANK, id_="1")