Editor opens in native windows (one per file)

Real BrowserWindow per edited file with its own RPC instance, deduped by
sessionId+path. The same Angular bundle boots an editor-only root via
preload globals. Native close isn't cancellable in electrobun, so the
editor mirrors its draft to bun; traffic-light closes get a native
Save/Discard prompt after the fact, and failed saves park the draft in
the edit-leftovers dir. In-window closes (Cmd+W, Close) use a styled
prompt; the quit guard now also counts unsaved editors.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/shared/rpc.ts

@@ -11,12 +11,24 @@ import type {
 	TransferSnapshot,
 } from "./types";
 
+/** Everything an editor window needs to know about the file it hosts. */
+export interface EditorOpenContext {
+	sessionId: string;
+	path: string;
+	name: string;
+	sessionTitle: string;
+}
+
 // Structurally equivalent to electrobun's ElectrobunRPCSchema, written in
 // resolved form so this file stays importable from the Angular bundle without
 // pulling in bun-only type modules.
 //
 // bun.requests    = calls the webview makes, handled in src/bun/rpc-handlers.ts
 // webview.messages = push events from bun, handled in ui rpc.service.ts
+//
+// ONE schema serves both window kinds (main + editor): electrobun allows
+// partial handler sets, and messages nobody listens to are silently dropped,
+// so each side only implements/hears what applies to it.
 export type AppRPC = {
 	bun: {
 		requests: {
@@ -122,8 +134,17 @@ export type AppRPC = {
 				response: Result;
 			};
 			moveToTrash: { params: { path: string }; response: Result };
+			// editor windows
+			/** Main window only: open (or focus) a native editor window. */
+			openEditor: { params: EditorOpenContext; response: Result };
+			/** Editor windows only — handled by that window's own rpc closure. */
+			editorSave: { params: { content: string }; response: Result };
+			editorClose: { params: Record<string, never>; response: Result };
+		};
+		messages: {
+			/** Editor → bun draft mirror; safety net for the non-cancellable native close. */
+			editorState: { dirty: boolean; content: string };
 		};
-		messages: Record<never, never>;
 	};
 	webview: {
 		requests: Record<never, never>;
@@ -131,6 +152,12 @@ export type AppRPC = {
 			transferUpdate: TransferSnapshot;
 			sessionClosed: { sessionId: string; reason: string };
 			menuAction: { action: string };
+			/** bun → editor windows when the main window saves settings. */
+			settingsChanged: { settings: AppSettings };
+			/** bun → main after an editor save, so matching panels refresh. */
+			pathRefresh: { sessionId: string; dir: string };
+			/** bun → one editor: run the in-window close flow (dirty prompt). */
+			editorCloseRequest: Record<string, never>;
 		};
 	};
 };