Feat v0.8.2 capability negotiation (#69)

Extensions declare environment requirements via capabilities.required and
capabilities.optional in their manifest. The kernel validates at install
time — required capabilities reject with HTTP 422 and rollback, optional
capabilities log a warning. Runtime query via settings.has_capability().
Admin endpoint GET /api/v1/admin/capabilities re-probes live.

Detected capabilities: postgres, pgvector, object_storage, s3, workspace.

18 new tests, all passing with -race.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/handlers/capabilities_test.go

@@ -0,0 +1,205 @@
+package handlers
+
+import (
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/gin-gonic/gin"
+)
+
+// ── ParseCapabilities ───────────────────────────────────────────────
+
+func TestParseCapabilities_Full(t *testing.T) {
+	manifest := map[string]any{
+		"id": "test-pkg",
+		"capabilities": map[string]any{
+			"required": []any{"postgres", "pgvector"},
+			"optional": []any{"s3"},
+		},
+	}
+	caps, ok := ParseCapabilities(manifest)
+	if !ok {
+		t.Fatal("expected ok=true")
+	}
+	if len(caps.Required) != 2 || caps.Required[0] != "postgres" || caps.Required[1] != "pgvector" {
+		t.Errorf("required = %v, want [postgres pgvector]", caps.Required)
+	}
+	if len(caps.Optional) != 1 || caps.Optional[0] != "s3" {
+		t.Errorf("optional = %v, want [s3]", caps.Optional)
+	}
+}
+
+func TestParseCapabilities_Missing(t *testing.T) {
+	manifest := map[string]any{"id": "test-pkg"}
+	_, ok := ParseCapabilities(manifest)
+	if ok {
+		t.Error("expected ok=false when no capabilities block")
+	}
+}
+
+func TestParseCapabilities_EmptyArrays(t *testing.T) {
+	manifest := map[string]any{
+		"capabilities": map[string]any{
+			"required": []any{},
+			"optional": []any{},
+		},
+	}
+	caps, ok := ParseCapabilities(manifest)
+	if !ok {
+		t.Fatal("expected ok=true")
+	}
+	if len(caps.Required) != 0 {
+		t.Errorf("required should be empty, got %v", caps.Required)
+	}
+	if len(caps.Optional) != 0 {
+		t.Errorf("optional should be empty, got %v", caps.Optional)
+	}
+}
+
+func TestParseCapabilities_IgnoresEmpty(t *testing.T) {
+	manifest := map[string]any{
+		"capabilities": map[string]any{
+			"required": []any{"pgvector", "", "postgres"},
+		},
+	}
+	caps, _ := ParseCapabilities(manifest)
+	if len(caps.Required) != 2 {
+		t.Errorf("expected 2 entries (empty filtered), got %v", caps.Required)
+	}
+}
+
+// ── CheckRequiredCapabilities ───────────────────────────────────────
+
+func TestCheckRequired_AllMet(t *testing.T) {
+	detected := map[string]bool{"postgres": true, "pgvector": true, "s3": true}
+	missing := CheckRequiredCapabilities([]string{"postgres", "pgvector"}, detected)
+	if len(missing) != 0 {
+		t.Errorf("expected no missing, got %v", missing)
+	}
+}
+
+func TestCheckRequired_SomeUnmet(t *testing.T) {
+	detected := map[string]bool{"postgres": true, "pgvector": false, "s3": false}
+	missing := CheckRequiredCapabilities([]string{"postgres", "pgvector", "s3"}, detected)
+	if len(missing) != 2 {
+		t.Errorf("expected 2 missing, got %v", missing)
+	}
+}
+
+func TestCheckRequired_EmptyRequired(t *testing.T) {
+	detected := map[string]bool{"postgres": true}
+	missing := CheckRequiredCapabilities(nil, detected)
+	if len(missing) != 0 {
+		t.Errorf("expected no missing for nil required, got %v", missing)
+	}
+}
+
+func TestCheckRequired_UnknownCap(t *testing.T) {
+	detected := map[string]bool{"postgres": true}
+	missing := CheckRequiredCapabilities([]string{"gpu"}, detected)
+	if len(missing) != 1 || missing[0] != "gpu" {
+		t.Errorf("expected [gpu], got %v", missing)
+	}
+}
+
+// ── capabilityHelpText ──────────────────────────────────────────────
+
+func TestCapabilityHelpText_KnownCaps(t *testing.T) {
+	hints := capabilityHelpText([]string{"pgvector", "s3"})
+	if len(hints) != 2 {
+		t.Fatalf("expected 2 hints, got %d", len(hints))
+	}
+	if hints["pgvector"] == "" {
+		t.Error("pgvector hint is empty")
+	}
+	if hints["s3"] == "" {
+		t.Error("s3 hint is empty")
+	}
+}
+
+func TestCapabilityHelpText_UnknownCap(t *testing.T) {
+	hints := capabilityHelpText([]string{"gpu"})
+	if hints["gpu"] == "" {
+		t.Error("expected fallback hint for unknown cap")
+	}
+}
+
+// ── DetectCapabilities (SQLite path — no real DB) ───────────────────
+
+func TestDetectCapabilities_SQLite_NilStore(t *testing.T) {
+	caps := DetectCapabilities(nil, false, nil, "")
+	if caps["postgres"] {
+		t.Error("postgres should be false on SQLite")
+	}
+	if caps["pgvector"] {
+		t.Error("pgvector should be false on SQLite")
+	}
+	if caps["object_storage"] {
+		t.Error("object_storage should be false with nil store")
+	}
+	if caps["s3"] {
+		t.Error("s3 should be false with nil store")
+	}
+	if caps["workspace"] {
+		t.Error("workspace should be false with empty root")
+	}
+}
+
+func TestDetectCapabilities_WorkspaceWritable(t *testing.T) {
+	tmpDir := t.TempDir()
+	caps := DetectCapabilities(nil, false, nil, tmpDir)
+	if !caps["workspace"] {
+		t.Error("workspace should be true for writable temp dir")
+	}
+}
+
+func TestDetectCapabilities_WorkspaceUnwritable(t *testing.T) {
+	caps := DetectCapabilities(nil, false, nil, "/nonexistent/path/xyz")
+	if caps["workspace"] {
+		t.Error("workspace should be false for nonexistent path")
+	}
+}
+
+// ── Admin endpoint ──────────────────────────────────────────────────
+
+func TestGetCapabilities_HTTP(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	h := NewCapabilitiesHandler(func() map[string]bool {
+		return map[string]bool{
+			"postgres":       false,
+			"pgvector":       false,
+			"object_storage": true,
+			"s3":             false,
+			"workspace":      true,
+		}
+	})
+
+	r := gin.New()
+	r.GET("/api/v1/admin/capabilities", h.GetCapabilities)
+
+	req := httptest.NewRequest(http.MethodGet, "/api/v1/admin/capabilities", nil)
+	w := httptest.NewRecorder()
+	r.ServeHTTP(w, req)
+
+	if w.Code != 200 {
+		t.Fatalf("status = %d, want 200", w.Code)
+	}
+
+	var result map[string]bool
+	if err := json.Unmarshal(w.Body.Bytes(), &result); err != nil {
+		t.Fatalf("unmarshal: %v", err)
+	}
+
+	if result["postgres"] {
+		t.Error("postgres should be false")
+	}
+	if !result["object_storage"] {
+		t.Error("object_storage should be true")
+	}
+	if !result["workspace"] {
+		t.Error("workspace should be true")
+	}
+}