engine: bounds and validation for the new forwarding levers

Novelty, HarmAwareness and ProgramEffect each get a 0..1 realism bound,
served in ConfigBounds and enforced in ValidateConfig with field-named
errors (the frontend matches on the JSON name to flag the right control).
Reject/boundary test cases added.

internal/engine/bounds_test.go

@@ -29,6 +29,12 @@ func TestValidateConfigRejectsOutOfBounds(t *testing.T) {
 		{"triangle probability above one", func(c *Config) { c.TriangleProb = 1.1 }, "triangleProb"},
 		{"negative forward probability", func(c *Config) { c.ForwardProb = -0.1 }, "forwardProb"},
 		{"guaranteed forwarding", func(c *Config) { c.ForwardProb = 0.95 }, "forwardProb"},
+		{"negative novelty", func(c *Config) { c.Novelty = -0.1 }, "novelty"},
+		{"novelty above one", func(c *Config) { c.Novelty = 1.1 }, "novelty"},
+		{"negative harm awareness", func(c *Config) { c.HarmAwareness = -0.1 }, "harmAwareness"},
+		{"harm awareness above one", func(c *Config) { c.HarmAwareness = 1.1 }, "harmAwareness"},
+		{"negative program effect", func(c *Config) { c.ProgramEffect = -0.1 }, "programEffect"},
+		{"program effect above one", func(c *Config) { c.ProgramEffect = 1.1 }, "programEffect"},
 		{"negative education budget", func(c *Config) { c.NumEducated = -1 }, "numEducated"},
 		{"educating more students than exist", func(c *Config) { c.NumEducated = 121 }, "numEducated"},
 		{"negative origin", func(c *Config) { c.Origin = -1 }, "origin"},
@@ -59,6 +65,9 @@ func TestValidateConfigAcceptsBoundaryValues(t *testing.T) {
 	config.EdgesPerNode = bounds.EdgesPerNode.Max
 	config.ForwardProb = bounds.ForwardProb.Max
 	config.TriangleProb = bounds.TriangleProb.Max
+	config.Novelty = bounds.Novelty.Max
+	config.HarmAwareness = bounds.HarmAwareness.Max
+	config.ProgramEffect = bounds.ProgramEffect.Max
 	config.NumEducated = config.NumStudents
 	config.Origin = config.NumStudents - 1
 	if err := ValidateConfig(config); err != nil {

internal/engine/scenario.go

@@ -108,10 +108,13 @@ type FloatBounds struct {
 // rate. numEducated and origin are relational (0..numStudents and
 // 0..numStudents-1) and therefore not listed; seeds are unrestricted.
 type Bounds struct {
-	NumStudents  IntBounds   `json:"numStudents"`
+	NumStudents   IntBounds   `json:"numStudents"`
-	EdgesPerNode IntBounds   `json:"edgesPerNode"`
+	EdgesPerNode  IntBounds   `json:"edgesPerNode"`
-	TriangleProb FloatBounds `json:"triangleProb"`
+	TriangleProb  FloatBounds `json:"triangleProb"`
-	ForwardProb  FloatBounds `json:"forwardProb"`
+	ForwardProb   FloatBounds `json:"forwardProb"`
+	Novelty       FloatBounds `json:"novelty"`
+	HarmAwareness FloatBounds `json:"harmAwareness"`
+	ProgramEffect FloatBounds `json:"programEffect"`
 }
 
 // ConfigBounds returns the bounds the engine enforces. The frontend
@@ -119,10 +122,13 @@ type Bounds struct {
 // sliders and clamping from the same numbers.
 func ConfigBounds() Bounds {
 	return Bounds{
-		NumStudents:  IntBounds{Min: 10, Max: 500},
+		NumStudents:   IntBounds{Min: 10, Max: 500},
-		EdgesPerNode: IntBounds{Min: 1, Max: 8},
+		EdgesPerNode:  IntBounds{Min: 1, Max: 8},
-		TriangleProb: FloatBounds{Min: 0, Max: 1},
+		TriangleProb:  FloatBounds{Min: 0, Max: 1},
-		ForwardProb:  FloatBounds{Min: 0, Max: 0.9},
+		ForwardProb:   FloatBounds{Min: 0, Max: 0.9},
+		Novelty:       FloatBounds{Min: 0, Max: 1},
+		HarmAwareness: FloatBounds{Min: 0, Max: 1},
+		ProgramEffect: FloatBounds{Min: 0, Max: 1},
 	}
 }
 
@@ -147,6 +153,18 @@ func ValidateConfig(config Config) error {
 		return fmt.Errorf("scenario: need %v <= forwardProb <= %v, got %v",
 			bounds.ForwardProb.Min, bounds.ForwardProb.Max, config.ForwardProb)
 	}
+	if config.Novelty < bounds.Novelty.Min || config.Novelty > bounds.Novelty.Max {
+		return fmt.Errorf("scenario: need %v <= novelty <= %v, got %v",
+			bounds.Novelty.Min, bounds.Novelty.Max, config.Novelty)
+	}
+	if config.HarmAwareness < bounds.HarmAwareness.Min || config.HarmAwareness > bounds.HarmAwareness.Max {
+		return fmt.Errorf("scenario: need %v <= harmAwareness <= %v, got %v",
+			bounds.HarmAwareness.Min, bounds.HarmAwareness.Max, config.HarmAwareness)
+	}
+	if config.ProgramEffect < bounds.ProgramEffect.Min || config.ProgramEffect > bounds.ProgramEffect.Max {
+		return fmt.Errorf("scenario: need %v <= programEffect <= %v, got %v",
+			bounds.ProgramEffect.Min, bounds.ProgramEffect.Max, config.ProgramEffect)
+	}
 	if config.NumEducated < 0 || config.NumEducated > config.NumStudents {
 		return fmt.Errorf("scenario: need 0 <= numEducated <= %d students, got %d",
 			config.NumStudents, config.NumEducated)