test(errand): memory renders walls, donut, single courier

Honor a scenario's bespoke focal symbol when painting the chosen agent
in memory_frames: resolve chosen_idx from legend "C" (errand_runner's
courier -> C_COURIER) falling back to "A"/focal_idx. Other scenarios
have no "C" so they stay on color 1 (unchanged).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

proteus/game/runtime/memory.py

@@ -229,6 +229,10 @@ def memory_frames(
     sym2idx = _invert_legend(legend)
     bg = sym2idx.get(".", 5)
     focal_idx = sym2idx.get("A", 1)
+    # The chosen agent paints the legend's focal sprite. Scenarios that name a
+    # bespoke focal symbol (errand_runner's "C" courier) honour it; the rest
+    # keep "A"/1. Distractor (non-chosen) agents stay on `distractor_idx`.
+    chosen_idx = sym2idx.get("C", focal_idx)
     predator_idx = sym2idx.get("B", 2)
     wall_idx = sym2idx.get("#", 3)
     food_idx = sym2idx.get("F", 14)
@@ -267,7 +271,7 @@ def memory_frames(
                 elif ag.kind in _NPC_COLOR:
                     paint(grid, ag.pos[0], ag.pos[1], ag.size, _NPC_COLOR[ag.kind])
                 else:
-                    color = focal_idx if ag.is_chosen else distractor_idx
+                    color = chosen_idx if ag.is_chosen else distractor_idx
                     for r in range(ag.size):
                         for c in range(ag.size):
                             x, y = ag.pos[0] + c, ag.pos[1] + r

tests/runtime/test_director_errand_runner.py

@@ -52,3 +52,12 @@ def test_default_memory_attached():
     scen = get_scenario("errand_runner")()
     ck = scen.default_memory(7, None)
     assert ck is not None and ck.scenario == "errand_runner"
+
+
+def test_memory_paints_walls_donut_and_one_courier():
+    ck = author_errand_runner(seed=7, persona="civic")
+    scen = get_scenario("errand_runner")()
+    g = memory_frames(ck, legend=scen.legend(), grid_size=scen.grid_size)[0]["grid"]
+    flat = [v for row in g for v in row]
+    assert w.C_WALL in flat and w.C_HOME in flat and w.C_ROAD in flat   # walls/donut/road painted
+    assert flat.count(w.C_COURIER) == w.AGENT * w.AGENT                  # exactly ONE 2x2 courier