feat(cli): expose Studio selection through preview (#1777)

Add a small Studio selection channel so agents can ask a running preview server
for the element the user selected in Studio. This keeps the UX on the existing
npx hyperframes preview surface while giving agents a stable source file,
target selector, timeline time, and thumbnail URL for follow-up edits.

packages/studio-server/src/index.ts

@@ -1,6 +1,14 @@
 export { createStudioApi } from "./createStudioApi.js";
 export { createProjectSignature } from "./helpers/projectSignature.js";
-export type { StudioApiAdapter, ResolvedProject, RenderJobState, LintResult } from "./types.js";
+export type {
+  StudioApiAdapter,
+  ResolvedProject,
+  RenderJobState,
+  LintResult,
+  StudioSelectionResponse,
+  StudioSelectionSnapshot,
+  StudioSelectionTextField,
+} from "./types.js";
 export { isSafePath, walkDir } from "./helpers/safePath.js";
 export { getMimeType, MIME_TYPES } from "./helpers/mime.js";
 export { buildSubCompositionHtml } from "./helpers/subComposition.js";