feat(plugins): add theme contributions

Adds plugin-contributed light and dark app themes, including persistence, host-aware coalescing, fallback behavior, documentation, examples, and browser/iOS QA.

packages/plugin/src/contracts.ts

@@ -102,6 +102,24 @@ export interface PluginSidebarContribution {
   surface: string;
 }
 
+export interface PluginThemeColors {
+  background: string;
+  foreground: string;
+  raised: string;
+  control: string;
+  border: string;
+  accent?: string;
+  mutedForeground: string;
+  ring: string;
+}
+
+export interface PluginThemeContribution {
+  id: string;
+  name: string;
+  appearance: "light" | "dark";
+  colors: PluginThemeColors;
+}
+
 export interface PluginAttachmentSourceContribution {
   id: string;
   title: string;
@@ -175,6 +193,7 @@ export interface PluginContext {
   addWorkspacePanel(contribution: PluginWorkspacePanelContribution): void;
   addCommandCenterItem(contribution: PluginCommandCenterItemContribution): void;
   addAttachmentSource(contribution: PluginAttachmentSourceContribution): void;
+  addTheme(contribution: PluginThemeContribution): void;
 }
 
 export type PluginCleanup = () => void | Promise<void>;

packages/plugin/src/host.ts

@@ -7,6 +7,7 @@ import type {
   PluginSidebarContribution,
   PluginSurfaceContribution,
   PluginSurfaceProps,
+  PluginThemeContribution,
   PluginWorkspacePanelContribution,
 } from "./contracts.js";
 import { PluginRpcProvider } from "./rpc-context.js";
@@ -20,6 +21,7 @@ interface PluginCollector {
   addWorkspacePanel(contribution: PluginWorkspacePanelContribution): void;
   addCommandCenterItem(contribution: PluginCommandCenterItemContribution): void;
   addAttachmentSource(contribution: PluginAttachmentSourceContribution): void;
+  addTheme(contribution: PluginThemeContribution): void;
 }
 
 export interface PluginRegistrationCollector {
@@ -28,6 +30,7 @@ export interface PluginRegistrationCollector {
   workspacePanels: PluginWorkspacePanelContribution[];
   commandCenterItems: PluginCommandCenterItemContribution[];
   attachmentSources: PluginAttachmentSourceContribution[];
+  themes: PluginThemeContribution[];
 }
 
 export function createPluginContext(
@@ -39,6 +42,7 @@ export function createPluginContext(
   | "addWorkspacePanel"
   | "addCommandCenterItem"
   | "addAttachmentSource"
+  | "addTheme"
 > {
   return {
     addSurface(id, Component) {
@@ -56,6 +60,9 @@ export function createPluginContext(
     addAttachmentSource(contribution) {
       collector.addAttachmentSource(contribution);
     },
+    addTheme(contribution) {
+      collector.addTheme(contribution);
+    },
   };
 }
 

packages/plugin/src/index.ts

@@ -24,6 +24,8 @@ export type {
   PluginSidebarContribution,
   PluginSurfaceContribution,
   PluginSurfaceProps,
+  PluginThemeColors,
+  PluginThemeContribution,
   PluginWorkspaceCommandContext,
   PluginWorkspacePanelContribution,
   PluginWorkspacePanelProps,