feat: extract coverage-gate action from Cue for reuse across projects

- Move coveragegate tool from cue/tools to vociferate/coverage-gate
- Create composite action with JSON metrics output for CI
- Update tool to export passes/total_coverage/packages_checked/packages_failed
- Support per-package threshold policy via JSON configuration
- Change module path to git.hrafn.xyz/aether/vociferate/coverage-gate

coverage-gate/parse_test.go

@@ -0,0 +1,88 @@
+package main
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestParseCoverProfile_AppliesExclusions(t *testing.T) {
+	t.Parallel()
+	tmp := t.TempDir()
+	profile := filepath.Join(tmp, "coverage.out")
+	content := "mode: set\n" +
+		"git.hrafn.xyz/aether/cue/api/graph/generated.go:1.1,2.1 2 1\n" +
+		"git.hrafn.xyz/aether/cue/api/graph/resolver.go:1.1,2.1 2 1\n" +
+		"git.hrafn.xyz/aether/cue/service/llm/validator.go:1.1,2.1 2 0\n"
+	if err := os.WriteFile(profile, []byte(content), 0600); err != nil {
+		t.Fatalf("write profile: %v", err)
+	}
+
+	policy := Policy{
+		MinimumStatementCoverage: 80,
+		CriticalPackages: []PackagePolicy{
+			{Package: "git.hrafn.xyz/aether/cue/api/graph", Include: true, Exclusions: []string{"generated.go"}},
+		},
+	}
+
+	got, err := ParseCoverProfile(profile, policy)
+	if err != nil {
+		t.Fatalf("ParseCoverProfile() error = %v", err)
+	}
+
+	api := got["git.hrafn.xyz/aether/cue/api/graph"]
+	if api.Total != 2 || api.Covered != 2 {
+		t.Fatalf("api coverage mismatch: got %+v", api)
+	}
+	llm := got["git.hrafn.xyz/aether/cue/service/llm"]
+	if llm.Total != 2 || llm.Covered != 0 {
+		t.Fatalf("llm coverage mismatch: got %+v", llm)
+	}
+}
+
+func TestEvaluateCoverage_UsesPolicyThresholds(t *testing.T) {
+	t.Parallel()
+	pkgs := []string{
+		"git.hrafn.xyz/aether/cue/service/llm",
+		"git.hrafn.xyz/aether/cue/service/orchestrator",
+	}
+	byPkg := map[string]Coverage{
+		"git.hrafn.xyz/aether/cue/service/llm":          {Covered: 8, Total: 10},
+		"git.hrafn.xyz/aether/cue/service/orchestrator": {Covered: 3, Total: 10},
+	}
+	policy := Policy{
+		MinimumStatementCoverage: 80,
+		CriticalPackages: []PackagePolicy{
+			{Package: "git.hrafn.xyz/aether/cue/service/orchestrator", MinimumStatementCoverage: 30, Include: true},
+		},
+	}
+
+	results := EvaluateCoverage(pkgs, byPkg, policy)
+	if len(results) != 2 {
+		t.Fatalf("expected 2 results, got %d", len(results))
+	}
+	if !results[0].Pass {
+		t.Fatalf("expected llm to pass at default threshold: %+v", results[0])
+	}
+	if !results[1].Pass {
+		t.Fatalf("expected orchestrator to pass at overridden threshold: %+v", results[1])
+	}
+}
+
+func TestEvaluateCoverage_NoStatementsPasses(t *testing.T) {
+	t.Parallel()
+
+	pkg := "git.hrafn.xyz/aether/cue/repository/vector"
+	results := EvaluateCoverage(
+		[]string{pkg},
+		map[string]Coverage{pkg: {Covered: 0, Total: 0}},
+		Policy{MinimumStatementCoverage: 80},
+	)
+
+	if len(results) != 1 {
+		t.Fatalf("expected 1 result, got %d", len(results))
+	}
+	if !results[0].Pass {
+		t.Fatalf("expected pass for no-statement package, got %+v", results[0])
+	}
+}