refactor(routing): clarify Floor/Ceil semantics + extend test coverage

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/config/routing.go

@@ -16,6 +16,12 @@ type RoutingConfig struct {
 	BrainURL           string  // BRAIN_URL, default http://ingestion.supervisor:3300
 	LocalModel         string  // HYPERGUILD_LOCAL_MODEL, default qwen35
 	ClaudeModel        string  // HYPERGUILD_CLAUDE_MODEL, default claude-sonnet-4-6
+	// RouteLocalFloor and RouteLocalCeil intentionally invert the usual
+	// floor < ceil mathematical convention: Floor (default 0.90) is the
+	// UPPER boundary — at/above it, always route local; Ceil (default 0.70)
+	// is the LOWER boundary — below it, always route Claude. The band in
+	// between is the 50/50 sample zone. The naming follows the spec's policy
+	// vocabulary; see internal/routing/policy.go for the consumer.
 	RouteLocalFloor    float64 // HYPERGUILD_ROUTE_LOCAL_FLOOR, default 0.90
 	RouteLocalCeil     float64 // HYPERGUILD_ROUTE_LOCAL_CEIL, default 0.70
 	PassRateTTLSeconds int     // HYPERGUILD_PASS_RATE_TTL_SECONDS, default 60

internal/config/routing_test.go

@@ -29,6 +29,7 @@ func TestLoadRoutingDefaults(t *testing.T) {
 	assert.InDelta(t, 0.90, cfg.RouteLocalFloor, 1e-9)
 	assert.InDelta(t, 0.70, cfg.RouteLocalCeil, 1e-9)
 	assert.Equal(t, 60, cfg.PassRateTTLSeconds)
+	assert.Equal(t, "", cfg.LiteLLMAPIKey)
 }
 
 func TestLoadRoutingFromEnv(t *testing.T) {
@@ -63,3 +64,10 @@ func TestLoadRoutingRejectsBadFloat(t *testing.T) {
 	require.Error(t, err)
 	assert.Contains(t, err.Error(), "HYPERGUILD_ROUTE_LOCAL_FLOOR")
 }
+
+func TestLoadRoutingRejectsBadInt(t *testing.T) {
+	t.Setenv("HYPERGUILD_PASS_RATE_TTL_SECONDS", "not-a-number")
+	_, err := config.LoadRouting()
+	require.Error(t, err)
+	assert.Contains(t, err.Error(), "HYPERGUILD_PASS_RATE_TTL_SECONDS")
+}