feat(pipeline): forest Right-variant baker (POC flow restyle, productionized)

Right strength curve (level 1-4 -> increasing img2img keyframe strength) is pure
and unit-tested; the restyle engine is a verbatim port of the session-0008 POC
flow_restyle.py (SD img2img keyframes + Farneback optical-flow tweens = calm,
no boiling). torch/diffusers imported lazily so the module + curve test stay light.

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

tests/test_bake_right_variants.py

@@ -0,0 +1,26 @@
+import pytest
+
+from simulator.bake_right_variants import RIGHT_LEVELS, right_strength_params
+
+
+def test_levels_are_one_through_four():
+    assert RIGHT_LEVELS == (1, 2, 3, 4)
+
+
+def test_strength_increases_with_level():
+    keys = [right_strength_params(l)[0] for l in RIGHT_LEVELS]
+    assert keys == sorted(keys)            # monotonic ramp
+    assert keys[0] < keys[-1]              # subtle -> strong
+
+
+def test_tween_strength_is_a_fraction_of_key_strength():
+    for l in RIGHT_LEVELS:
+        key, tween = right_strength_params(l)
+        assert 0.0 < tween < key           # tween is a light refine only
+
+
+def test_rejects_out_of_range_level():
+    with pytest.raises(ValueError):
+        right_strength_params(0)
+    with pytest.raises(ValueError):
+        right_strength_params(5)