fix(rules): line spells stop at a line-of-effect barrier (SRD aiming-a-spell.md: a line 'extends to the limit of its range or until it strikes a barrier that blocks line of effect') - line_cells truncates at the first blocks_los cell, creatures behind a solid wall are never caught

src/pf1e_simulator/areas.py

@@ -14,8 +14,12 @@ PF1e (CRB, Magic — Aiming a Spell):
   line's length. The line "starts from any corner of your square", so the
   CASTER's own square is NOT one of the affected squares: the affected
   squares are the ones beyond the origin along the ray (SRD Lightning Bolt:
-  "The bolt begins at your fingertips" — it leaves your square, it does not
-  fill it).
+  "The bolt begins at your fingertips" - it leaves your square, it does not
+  fill it). The line also stops at the first square that blocks line of
+  effect (CRB, Magic - Aiming a Spell, Line: it "extends to the limit of its
+  range or until it strikes a barrier that blocks line of effect"): the
+  barrier square itself and everything beyond it are outside the template,
+  so a bolt never reaches creatures behind a solid wall.
 
 Bursts need no template here: they are circles around a center cell and are
 resolved by ``CombatEngine._creatures_in_range`` (unchanged).
@@ -78,10 +82,13 @@ def line_cells(
     The line runs along the Bresenham ray from the origin toward ``aim``,
     extended to ``length_cells`` squares (CRB: it "extends to the limit of
     its range"). The line "starts from any corner of your square" (CRB, Magic
-    — Aiming a Spell), so the CASTER's own square is NOT affected: the
+    - Aiming a Spell), so the CASTER's own square is NOT affected: the
     ``length_cells`` affected squares are the ones *beyond* the origin along
     the ray. Out-of-bounds cells simply drop out of the template (creatures
-    only exist in bounds). A degenerate aim (origin == aim) affects nothing.
+    only exist in bounds). The ray stops at the first cell that blocks line
+    of effect (CRB, Line: "or until it strikes a barrier that blocks line of
+    effect") - that barrier cell and everything beyond it are excluded. A
+    degenerate aim (origin == aim) affects nothing.
     """
     if length_cells <= 0:
         return frozenset()
@@ -98,7 +105,14 @@ def line_cells(
     # 120 ft / 5 ft = 24 squares, none of them the caster's own (SRD Lightning
     # Bolt: "The bolt begins at your fingertips" — it leaves your square).
     ray = _bresenham(origin, end)
-    return frozenset(cell for cell in ray[1 : length_cells + 1] if grid.in_bounds(cell))
+    cells: list[Pos] = []
+    for cell in ray[1 : length_cells + 1]:
+        if not grid.in_bounds(cell):
+            continue
+        if grid.terrain_at(cell).blocks_los:
+            break
+        cells.append(cell)
+    return frozenset(cells)
 
 
 def _bresenham(start: Pos, end: Pos) -> list[Pos]: