refactor: Modularize Electron main process into single-responsibility components

Extract the monolithic main.ts (~1000 lines) into focused modules:

- electron/constants.ts - Window sizing, port defaults, filenames
- electron/state.ts - Shared state container
- electron/utils/ - Port availability and icon utilities
- electron/security/ - API key management
- electron/windows/ - Window bounds and main window creation
- electron/server/ - Backend and static server management
- electron/ipc/ - IPC handlers with shared channel constants

Benefits:
- Improved testability with isolated modules
- Better discoverability and maintainability
- Single source of truth for IPC channels (used by both main and preload)
- Clear separation of concerns

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/ui/src/electron/windows/window-bounds.ts

@@ -0,0 +1,130 @@
+/**
+ * Window bounds management
+ *
+ * Functions for loading, saving, and validating window bounds.
+ * Uses centralized electronUserData methods for path validation.
+ */
+
+import { screen } from 'electron';
+import {
+  electronUserDataExists,
+  electronUserDataReadFileSync,
+  electronUserDataWriteFileSync,
+} from '@automaker/platform';
+import { createLogger } from '@automaker/utils/logger';
+import {
+  WindowBounds,
+  WINDOW_BOUNDS_FILENAME,
+  MIN_WIDTH_COLLAPSED,
+  MIN_HEIGHT,
+} from '../constants';
+import { state } from '../state';
+
+const logger = createLogger('WindowBounds');
+
+/**
+ * Load saved window bounds from disk
+ * Uses centralized electronUserData methods for path validation.
+ */
+export function loadWindowBounds(): WindowBounds | null {
+  try {
+    if (electronUserDataExists(WINDOW_BOUNDS_FILENAME)) {
+      const data = electronUserDataReadFileSync(WINDOW_BOUNDS_FILENAME);
+      const bounds = JSON.parse(data) as WindowBounds;
+      // Validate the loaded data has required fields
+      if (
+        typeof bounds.x === 'number' &&
+        typeof bounds.y === 'number' &&
+        typeof bounds.width === 'number' &&
+        typeof bounds.height === 'number'
+      ) {
+        return bounds;
+      }
+    }
+  } catch (error) {
+    logger.warn('Failed to load window bounds:', (error as Error).message);
+  }
+  return null;
+}
+
+/**
+ * Save window bounds to disk
+ * Uses centralized electronUserData methods for path validation.
+ */
+export function saveWindowBounds(bounds: WindowBounds): void {
+  try {
+    electronUserDataWriteFileSync(WINDOW_BOUNDS_FILENAME, JSON.stringify(bounds, null, 2));
+    logger.info('Window bounds saved');
+  } catch (error) {
+    logger.warn('Failed to save window bounds:', (error as Error).message);
+  }
+}
+
+/**
+ * Schedule a debounced save of window bounds (500ms delay)
+ */
+export function scheduleSaveWindowBounds(): void {
+  if (!state.mainWindow || state.mainWindow.isDestroyed()) return;
+
+  if (state.saveWindowBoundsTimeout) {
+    clearTimeout(state.saveWindowBoundsTimeout);
+  }
+
+  state.saveWindowBoundsTimeout = setTimeout(() => {
+    if (!state.mainWindow || state.mainWindow.isDestroyed()) return;
+
+    const isMaximized = state.mainWindow.isMaximized();
+    // Use getNormalBounds() for maximized windows to save pre-maximized size
+    const bounds = isMaximized ? state.mainWindow.getNormalBounds() : state.mainWindow.getBounds();
+
+    saveWindowBounds({
+      x: bounds.x,
+      y: bounds.y,
+      width: bounds.width,
+      height: bounds.height,
+      isMaximized,
+    });
+  }, 500);
+}
+
+/**
+ * Validate that window bounds are visible on at least one display
+ * Returns adjusted bounds if needed, or null if completely off-screen
+ */
+export function validateBounds(bounds: WindowBounds): WindowBounds {
+  const displays = screen.getAllDisplays();
+
+  // Check if window center is visible on any display
+  const centerX = bounds.x + bounds.width / 2;
+  const centerY = bounds.y + bounds.height / 2;
+
+  let isVisible = false;
+  for (const display of displays) {
+    const { x, y, width, height } = display.workArea;
+    if (centerX >= x && centerX <= x + width && centerY >= y && centerY <= y + height) {
+      isVisible = true;
+      break;
+    }
+  }
+
+  if (!isVisible) {
+    // Window is off-screen, reset to primary display
+    const primaryDisplay = screen.getPrimaryDisplay();
+    const { x, y, width, height } = primaryDisplay.workArea;
+
+    return {
+      x: x + Math.floor((width - bounds.width) / 2),
+      y: y + Math.floor((height - bounds.height) / 2),
+      width: Math.min(bounds.width, width),
+      height: Math.min(bounds.height, height),
+      isMaximized: bounds.isMaximized,
+    };
+  }
+
+  // Ensure minimum dimensions
+  return {
+    ...bounds,
+    width: Math.max(bounds.width, MIN_WIDTH_COLLAPSED),
+    height: Math.max(bounds.height, MIN_HEIGHT),
+  };
+}