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/pages/pages.go

@@ -61,6 +61,20 @@ type SurfaceManifest struct {
 	Source       string   `json:"source"`        // "core" or "extension"
 }
 
+// PanelMeta describes a resolved panel available to a surface.
+type PanelMeta struct {
+	PanelID       string `json:"panel_id"`                 // e.g. "notes.reference"
+	PackageID     string `json:"package_id"`               // e.g. "notes"
+	Entry         string `json:"entry"`                    // e.g. "js/panels/reference.js"
+	Title         string `json:"title"`                    // human-readable
+	Icon          string `json:"icon,omitempty"`           // emoji or icon key
+	Description   string `json:"description,omitempty"`    // short description
+	MinWidth      int    `json:"min_width,omitempty"`      // minimum width in px
+	MinHeight     int    `json:"min_height,omitempty"`     // minimum height in px
+	DefaultWidth  int    `json:"default_width,omitempty"`  // default width in px
+	DefaultHeight int    `json:"default_height,omitempty"` // default height in px
+}
+
 // BannerConfig holds environment banner settings.
 type BannerConfig struct {
 	Text       string `json:"text"`
@@ -109,6 +123,8 @@ type PageData struct {
 
 	BrowserExtensions []string `json:"-"` // IDs of enabled browser-tier extensions (for script injection)
 
+	Panels []PanelMeta `json:"-"` // resolved panels available to this surface
+
 	InstanceName     string // branding: instance display name
 	LogoURL          string // branding: custom logo URL
 	Tagline          string // branding: tagline under instance name
@@ -237,6 +253,72 @@ func (e *Engine) browserExtensionIDs() []string {
 	return ids
 }
 
+// resolvePanels reads the consumer's panels array from the raw manifest and
+// resolves each reference against installed+enabled provider packages.
+// Returns nil if no panels are declared or no providers are available.
+func (e *Engine) resolvePanels(ctx context.Context, manifest map[string]any) []PanelMeta {
+	if e.stores.Packages == nil {
+		return nil
+	}
+	rawPanels, ok := manifest["panels"].([]any)
+	if !ok || len(rawPanels) == 0 {
+		return nil
+	}
+
+	var result []PanelMeta
+	for _, raw := range rawPanels {
+		ref, ok := raw.(string)
+		if !ok {
+			continue
+		}
+		parts := strings.SplitN(ref, ".", 2)
+		if len(parts) != 2 {
+			continue
+		}
+		pkgID, panelKey := parts[0], parts[1]
+
+		provPkg, err := e.stores.Packages.Get(ctx, pkgID)
+		if err != nil || provPkg == nil || !provPkg.Enabled {
+			continue
+		}
+
+		provPanels, ok := provPkg.Manifest["panels"].(map[string]any)
+		if !ok {
+			continue
+		}
+		panelDef, ok := provPanels[panelKey].(map[string]any)
+		if !ok {
+			continue
+		}
+
+		meta := PanelMeta{
+			PanelID:   ref,
+			PackageID: pkgID,
+		}
+		meta.Entry, _ = panelDef["entry"].(string)
+		meta.Title, _ = panelDef["title"].(string)
+		meta.Icon, _ = panelDef["icon"].(string)
+		meta.Description, _ = panelDef["description"].(string)
+		if v, ok := panelDef["min_width"].(float64); ok {
+			meta.MinWidth = int(v)
+		}
+		if v, ok := panelDef["min_height"].(float64); ok {
+			meta.MinHeight = int(v)
+		}
+		if v, ok := panelDef["default_width"].(float64); ok {
+			meta.DefaultWidth = int(v)
+		}
+		if v, ok := panelDef["default_height"].(float64); ok {
+			meta.DefaultHeight = int(v)
+		}
+
+		if meta.Entry != "" && meta.Title != "" {
+			result = append(result, meta)
+		}
+	}
+	return result
+}
+
 // UserContext is the authenticated user's info available to templates.
 type UserContext struct {
 	ID          string `json:"id"`
@@ -552,6 +634,7 @@ func (e *Engine) RenderExtensionSurface() gin.HandlerFunc {
 			EnabledSurfaces:   e.EnabledSurfaceIDs(),
 			ExtensionSurfaces: e.extensionNavItems(),
 			BrowserExtensions: e.browserExtensionIDs(),
+			Panels:            e.resolvePanels(c.Request.Context(), sr.Manifest),
 		})
 	}
 }