Feat v0.10.0 panel manifest lifecycle

Panels are a new kernel rendering tier between surfaces and block
renderers, enabling composable companion views (e.g. notes panel
inside chat). This version ships the plumbing layer:

- Manifest validation for panels field (provider map + consumer array)
- Soft-dep warning at install time for unresolved panel consumers
- PanelMeta struct + resolvePanels() resolves consumers at surface load
- window.__PANELS__ injected into base template
- sw.panels SDK module (open/close/toggle/isOpen/isAvailable/list/active)
- Lazy JS loading pipeline with module caching
- 10 new tests (6 validation + 4 resolve)

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

server/handlers/package_validate.go

@@ -38,6 +38,8 @@ type ManifestInfo struct {
 	RequiresRoles   []string // team roles needed to access this package (advisory, OR semantics)
 	Adoptable       bool     // if true, teams can adopt this package to get a team-scoped copy
 	HasFormTemplate bool     // if true, package declares a form_template at the top level
+	HasPanels       bool     // if true, package provides panels (provider form)
+	PanelConsumers  []string // panel IDs this package consumes (consumer form, e.g. "notes.reference")
 }
 
 // ValidateManifest parses a manifest map and validates all required fields,
@@ -199,6 +201,44 @@ func ValidateManifest(manifest map[string]any) (*ManifestInfo, error) {
 		info.HasFormTemplate = true
 	}
 
+	// v0.10.0: panels — provider (map) or consumer (array) declarations
+	if rawPanels := manifest["panels"]; rawPanels != nil {
+		switch p := rawPanels.(type) {
+		case map[string]any:
+			// Provider form: { "reference": { "entry": "...", "title": "..." }, ... }
+			for key, raw := range p {
+				panel, ok := raw.(map[string]any)
+				if !ok {
+					return nil, fmt.Errorf("panels.%s must be an object", key)
+				}
+				entry, _ := panel["entry"].(string)
+				if entry == "" {
+					return nil, fmt.Errorf("panels.%s requires an 'entry' field", key)
+				}
+				title, _ := panel["title"].(string)
+				if title == "" {
+					return nil, fmt.Errorf("panels.%s requires a 'title' field", key)
+				}
+			}
+			info.HasPanels = true
+		case []any:
+			// Consumer form: ["notes.reference", "notes.graph"]
+			for i, raw := range p {
+				s, ok := raw.(string)
+				if !ok || s == "" {
+					return nil, fmt.Errorf("panels[%d] must be a non-empty string", i)
+				}
+				parts := strings.SplitN(s, ".", 2)
+				if len(parts) != 2 || parts[0] == "" || parts[1] == "" {
+					return nil, fmt.Errorf("panels[%d] must be in 'package.panel' format, got %q", i, s)
+				}
+				info.PanelConsumers = append(info.PanelConsumers, s)
+			}
+		default:
+			return nil, fmt.Errorf("panels must be an object (provider) or array (consumer)")
+		}
+	}
+
 	info.SchemaVersion = ParseSchemaVersion(manifest)
 
 	// ── Type-specific constraints ────────────────────────────────