v1.2: overwrite confirm, transfer speed/ETA, settings + themes, fused macOS titlebar

- Overwrite confirmation: name-collision detection before enqueue; dialog shows
  source vs destination (size, mtime, 'newer' badge) with per-item Skip/Replace
  and batch Skip all / Replace all; type mismatches auto-skip with a toast;
  cancel aborts the whole operation
- Transfer speed + ETA: UI computes smoothed bytes/sec from progress deltas
  (callback bus makes deltas meaningful); shown in the expanded queue rows and
  the status-bar summary; unit follows the speed-unit setting
- Settings: bun-side SettingsStore (settings.json, 0600, atomic) + get/save RPC;
  SettingsService; gear popover on the tab row (theme segmented control, speed
  unit); persisted across restarts
- Light theme: data-theme on <html> drives token overrides; absent = follow OS
- macOS fused titlebar: hiddenInset + trafficLightOffset, tab row becomes the
  draggable titlebar (app-region drag/no-drag classes); other platforms keep a
  separate titlebar (gated by a platform value injected via window preload)
- README: known-issues note for the upstream Bun/Electrobun FFI crash

Verified: tsc + ui build clean; SettingsStore roundtrip + 0600 headless;
app boots and the UI fetches settings over RPC at startup.

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

src/bun/index.ts

@@ -3,6 +3,7 @@ import { BRANDING } from "../shared/branding";
 import { SessionRegistry } from "./fs/registry";
 import { createAppRPC } from "./rpc-handlers";
 import { ConnectionStore } from "./store/connections";
+import { SettingsStore } from "./store/settings";
 import { TransferEngine } from "./transfers/engine";
 
 const PROD_URL = "views://app/index.html";
@@ -28,10 +29,13 @@ async function getMainViewUrl(): Promise<string> {
 const registry = new SessionRegistry();
 const engine = new TransferEngine(registry);
 const store = new ConnectionStore();
+const settings = new SettingsStore();
 const events = { sessionClosed: (_info: { sessionId: string; reason: string }) => {} };
-const rpc = createAppRPC({ registry, engine, store, events });
+const rpc = createAppRPC({ registry, engine, store, settings, events });
 const url = await getMainViewUrl();
 
+const isMac = process.platform === "darwin";
+
 new BrowserWindow({
 	title: BRANDING.appName,
 	url,
@@ -41,6 +45,14 @@ new BrowserWindow({
 		x: 120,
 		y: 120,
 	},
+	// macOS: fuse the tab bar with the titlebar — traffic lights overlay the
+	// UI's h-10 tab row (offset centers them vertically). Other platforms keep
+	// the native titlebar and the tab bar stays a separate row.
+	...(isMac
+		? { titleBarStyle: "hiddenInset" as const, trafficLightOffset: { x: 12, y: 13 } }
+		: {}),
+	// lets the UI pick the fused layout before first paint
+	preload: `window.__BUNSCP_PLATFORM=${JSON.stringify(process.platform)};`,
 	rpc,
 });
 

src/bun/rpc-handlers.ts

@@ -4,6 +4,7 @@ import type { Result } from "../shared/types";
 import type { SessionRegistry } from "./fs/registry";
 import { SftpProvider } from "./fs/sftp";
 import type { ConnectionStore } from "./store/connections";
+import type { SettingsStore } from "./store/settings";
 import type { TransferEngine } from "./transfers/engine";
 import { removeRecursive } from "./transfers/walk";
 
@@ -15,6 +16,7 @@ export interface AppDeps {
 	registry: SessionRegistry;
 	engine: TransferEngine;
 	store: ConnectionStore;
+	settings: SettingsStore;
 	/** Assigned after the rpc object exists (it needs rpc.send). */
 	events: { sessionClosed: (info: { sessionId: string; reason: string }) => void };
 }
@@ -27,7 +29,7 @@ async function wrap<T extends object>(fn: () => Promise<T> | T): Promise<Result<
 	}
 }
 
-export function createAppRPC({ registry, engine, store, events }: AppDeps) {
+export function createAppRPC({ registry, engine, store, settings, events }: AppDeps) {
 	return BrowserView.defineRPC<AppRPC>({
 		maxRequestTime: MAX_REQUEST_TIME_MS,
 		handlers: {
@@ -135,6 +137,15 @@ export function createAppRPC({ registry, engine, store, events }: AppDeps) {
 						await store.deleteFolder(id);
 						return {};
 					}),
+
+				// ---- settings ----
+				getSettings: () => wrap(async () => ({ settings: await settings.load() })),
+
+				saveSettings: ({ settings: next }) =>
+					wrap(async () => {
+						await settings.save(next);
+						return {};
+					}),
 			},
 		},
 	});

src/bun/store/settings.ts

@@ -0,0 +1,25 @@
+import fs from "node:fs/promises";
+import path from "node:path";
+import { DEFAULT_SETTINGS, type AppSettings } from "../../shared/types";
+import { appDataDir } from "./paths";
+
+/** App settings persisted bun-side (WKWebView localStorage on views:// is unreliable). */
+export class SettingsStore {
+	private readonly file = path.join(appDataDir(), "settings.json");
+
+	async load(): Promise<AppSettings> {
+		try {
+			const data = JSON.parse(await fs.readFile(this.file, "utf8"));
+			return { ...DEFAULT_SETTINGS, ...data };
+		} catch {
+			return { ...DEFAULT_SETTINGS };
+		}
+	}
+
+	async save(settings: AppSettings): Promise<void> {
+		await fs.mkdir(path.dirname(this.file), { recursive: true });
+		const tmp = `${this.file}.tmp`;
+		await fs.writeFile(tmp, JSON.stringify(settings, null, "\t"), { mode: 0o600 });
+		await fs.rename(tmp, this.file);
+	}
+}

src/shared/rpc.ts

@@ -1,4 +1,5 @@
 import type {
+	AppSettings,
 	ConnFolder,
 	ConnectionConfig,
 	ConnectionsFile,
@@ -67,6 +68,12 @@ export type AppRPC = {
 			deleteConnection: { params: { id: string }; response: Result };
 			upsertFolder: { params: { folder: ConnFolder }; response: Result<{ id: string }> };
 			deleteFolder: { params: { id: string }; response: Result };
+			// settings
+			getSettings: {
+				params: Record<string, never>;
+				response: Result<{ settings: AppSettings }>;
+			};
+			saveSettings: { params: { settings: AppSettings }; response: Result };
 		};
 		messages: Record<never, never>;
 	};

src/shared/types.ts

@@ -41,6 +41,16 @@ export interface ConnectionsFile {
 	connections: SavedConnection[];
 }
 
+export interface AppSettings {
+	theme: "system" | "light" | "dark";
+	speedUnit: "MBps" | "Mbps";
+}
+
+export const DEFAULT_SETTINGS: AppSettings = {
+	theme: "system",
+	speedUnit: "MBps",
+};
+
 export type TransferState =
 	| "queued"
 	| "scanning"