P5: light-tier canary — gadfly-shaped reviewer on executus core

examples/reviewer proves the core is sufficient for a static-binary light host
(gadfly's shape) with NO batteries:
- config.Env + model.Configure  -> env-driven model fleet + tier overrides
- model.ParseModelForContext    -> tier resolution + failover
- fanout.Run (PerKey caps)      -> N models x M lenses swarm, per-provider bound
- model.GenerateWith[T]         -> structured findings per (model, lens) cell
- Consolidate                   -> one verdict-led report section per model

Hermetic test runs the full 2x3 swarm against majordomo's fake provider and
asserts the consolidated verdicts. A go list -deps CI check asserts the canary
imports ZERO batteries (the light-tier invariant) — gadfly's go.sum stays free
of gorm/redis/discordgo/sqlite. README + docs updated.

This is the canary; migrating the LIVE gadfly repo onto executus core is a
follow-up (kept separate to not destabilize the active reviewer).

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

examples/reviewer/reviewer_test.go

@@ -0,0 +1,102 @@
+package main
+
+import (
+	"context"
+	"strings"
+	"testing"
+
+	"gitea.stevedudenhoeffer.com/steve/majordomo/provider/fake"
+
+	"gitea.stevedudenhoeffer.com/steve/executus/fanout"
+)
+
+// TestReviewSwarm proves the light-tier path end-to-end against the fake
+// provider: a 2-model × 3-lens swarm runs, structured findings parse, and
+// consolidation produces one verdict-led section per model — no batteries, no
+// network.
+func TestReviewSwarm(t *testing.T) {
+	fp := fake.New("fakeprov")
+
+	// Model "hot" reports a high-severity finding on every lens; "cold" reports
+	// nothing. Each model is called once per lens (3×), so enqueue 3 each.
+	hot := `{"findings":[{"severity":"high","title":"SQL injection","detail":"unsanitized id in query"}]}`
+	cold := `{"findings":[]}`
+	for i := 0; i < 3; i++ {
+		fp.Enqueue("hot", fake.Reply(hot))
+		fp.Enqueue("cold", fake.Reply(cold))
+	}
+	hotM, err := fp.Model("hot")
+	if err != nil {
+		t.Fatal(err)
+	}
+	coldM, err := fp.Model("cold")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	models := []NamedModel{
+		{Name: "hot", Provider: "fakeprov", Model: hotM},
+		{Name: "cold", Provider: "fakeprov", Model: coldM},
+	}
+	lenses := []Lens{{Name: "security"}, {Name: "correctness"}, {Name: "error-handling"}}
+
+	results := Review(context.Background(), models, lenses, "some diff",
+		fanout.Options[cell]{MaxConcurrent: 6, PerKey: map[string]int{"fakeprov": 3}})
+
+	// 2 models × 3 lenses = 6 cells, all successful.
+	if len(results) != 6 {
+		t.Fatalf("got %d cells, want 6", len(results))
+	}
+	var hotFindings, coldFindings, errs int
+	for _, r := range results {
+		if r.Err != nil {
+			errs++
+			continue
+		}
+		switch r.Model {
+		case "hot":
+			hotFindings += len(r.Findings)
+		case "cold":
+			coldFindings += len(r.Findings)
+		}
+	}
+	if errs != 0 {
+		t.Errorf("expected no cell errors, got %d", errs)
+	}
+	if hotFindings != 3 { // one per lens
+		t.Errorf("hot model findings = %d, want 3", hotFindings)
+	}
+	if coldFindings != 0 {
+		t.Errorf("cold model findings = %d, want 0", coldFindings)
+	}
+
+	report := Consolidate(results)
+	if !strings.Contains(report, "hot — blocking issues found") {
+		t.Errorf("hot section should lead with a blocking verdict:\n%s", report)
+	}
+	if !strings.Contains(report, "cold — no issues found") {
+		t.Errorf("cold section should report no issues:\n%s", report)
+	}
+	if !strings.Contains(report, "SQL injection") {
+		t.Errorf("report should surface the finding:\n%s", report)
+	}
+}
+
+// TestConsolidateVerdicts checks the worst-severity-led header logic.
+func TestConsolidateVerdicts(t *testing.T) {
+	got := Consolidate([]LensResult{
+		{Model: "m", Lens: "a", Findings: []Finding{{Severity: SevSmall, Title: "x"}}},
+		{Model: "m", Lens: "b", Findings: []Finding{{Severity: SevMedium, Title: "y"}}},
+	})
+	if !strings.Contains(got, "m — minor issues") {
+		t.Errorf("medium-max should be 'minor issues', got:\n%s", got)
+	}
+	// An errored lens is surfaced in the header.
+	got = Consolidate([]LensResult{
+		{Model: "m", Lens: "a", Findings: []Finding{{Severity: SevCritical, Title: "boom"}}},
+		{Model: "m", Lens: "b", Err: context.DeadlineExceeded},
+	})
+	if !strings.Contains(got, "blocking issues found") || !strings.Contains(got, "errored") {
+		t.Errorf("critical + errored lens header wrong:\n%s", got)
+	}
+}