Fix Ctrl+Click for Macs, and alphabetize gitignore (#2720)

Resolves #2719 
- [X] Ran `npm run format`
- [X] Ran `npm run lint:fix`
- [X] Ran `npm test`
- [X] Manually tested fixes

## Description:

### What problem(s) was I solving?

On Mac, `Ctrl+Click` is commonly used as a substitute for right-click to
open context menus. However, in OpenFront, `Ctrl+Click` was triggering
both the context menu, AND causing an attack.

This effectively prevented Mac users from being able to ally with
bots/nations, as trying to ally would cause you to attack them.

### What changes did I make?
- `Ctrl+Click` on Mac no longer triggers an attack, allowing players to
properly interact with the alliance system

### How I implemented it

1. Added an `isMac()` method to `InputHandler` which encapsulates the
"is mac" logic, and lets it be mocked during tests
2. In the `onPointerUp` handler, added a check: if on Mac and
`ControlLeft` is held, emit a `ContextMenuEvent`, and then return
(instead of continuing to also create a `MouseUpEvent`)
3. Extracted magic numbers for mouse button checks into descriptive
helper methods (`isMiddleMouseButton`, `isNonLeftMouseButton`) for
improved code clarity
4. Added clarifying comments throughout the pointer event handlers

Last, alphabetized the `.gitignore` file and organized it into "Folders"
and "Files" sections to make it easier to read.

### How to verify it

#### Manual Testing
- [X] On a Mac, hold `Ctrl` and left-click on another nation - verify
the context menu opens (not an attack)
- [X] On a Mac, right-click should still open the context menu as
expected
- [X] On Windows/Linux, `Ctrl+Click` continue to work as before
(modifier key for build menu if configured)
- [X] Regular left-click still triggers attacks/interactions as expected

#### Automated Testing
- [x] New unit test added: `Mac Ctrl+Click Context Menu` - verifies that
`Ctrl+Click` on Mac emits `ContextMenuEvent` instead of `MouseUpEvent`

### Description for the changelog

Fixed `Ctrl+Click` on Mac to properly open the context menu instead of
triggering an attack, restoring the ability for Mac users to form
alliances with other nations.

## Please complete the following:

- [X] I have added screenshots for all UI updates
- [X] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [X] I have added relevant tests to the test directory
- [X] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced

## Please put your Discord username so you can be contacted if a bug or
regression is found:
Terekhov

src/client/InputHandler.ts

@@ -153,6 +153,12 @@ export class InputHandler {
   private activeKeys = new Set<string>();
   private keybinds: Record<string, string> = {};
 
+  private readonly isMacReal = /Mac/.test(navigator.userAgent);
+  isMac(): boolean {
+    // Method exists so we can mock during tests
+    return this.isMacReal;
+  }
+
   private readonly PAN_SPEED = 5;
   private readonly ZOOM_SPEED = 10;
 
@@ -186,9 +192,6 @@ export class InputHandler {
       console.warn("Invalid keybinds JSON:", e);
     }
 
-    // Mac users might have different keybinds
-    const isMac = /Mac/.test(navigator.userAgent);
-
     this.keybinds = {
       toggleView: "Space",
       centerCamera: "KeyC",
@@ -202,8 +205,9 @@ export class InputHandler {
       attackRatioUp: "KeyY",
       boatAttack: "KeyB",
       groundAttack: "KeyG",
+      // Mac users might have different keybinds
+      modifierKey: this.isMac() ? "MetaLeft" : "ControlLeft",
       swapDirection: "KeyU",
-      modifierKey: isMac ? "MetaLeft" : "ControlLeft",
       altKey: "AltLeft",
       buildCity: "Digit1",
       buildFactory: "Digit2",
@@ -448,13 +452,15 @@ export class InputHandler {
   }
 
   private onPointerDown(event: PointerEvent) {
-    if (event.button === 1) {
+    // Handle middle mouse button (wheel click) for auto-upgrade
+    if (this.isMiddleMouseButton(event.button)) {
       event.preventDefault();
       this.eventBus.emit(new AutoUpgradeEvent(event.clientX, event.clientY));
       return;
     }
 
-    if (event.button > 0) {
+    // Ignore right mouse button and other non-left buttons
+    if (!this.isLeftMouseButton(event.button)) {
       return;
     }
 
@@ -475,12 +481,14 @@ export class InputHandler {
   }
 
   onPointerUp(event: PointerEvent) {
-    if (event.button === 1) {
+    // Prevent default behavior for middle mouse button, but don't process further
+    if (this.isMiddleMouseButton(event.button)) {
       event.preventDefault();
       return;
     }
 
-    if (event.button > 0) {
+    // Ignore right mouse button and other non-left buttons
+    if (!this.isLeftMouseButton(event.button)) {
       return;
     }
     this.pointerDown = false;
@@ -490,15 +498,27 @@ export class InputHandler {
       this.eventBus.emit(new ShowBuildMenuEvent(event.clientX, event.clientY));
       return;
     }
+
     if (this.isAltKeyPressed(event)) {
       this.eventBus.emit(new ShowEmojiMenuEvent(event.clientX, event.clientY));
       return;
     }
 
+    // If Ctrl is held down (for example, on a Mac which doesn't have a right-click)
+    // then Ctrl+Click is used to open context menu.
+    //
+    // Without this conditional, Ctrl+click causes the player to attack someone
+    // if they are not allied, effectively removing ability to ally with bots/nations.
+    if (this.isMac() && this.activeKeys.has("ControlLeft")) {
+      this.eventBus.emit(new ContextMenuEvent(event.clientX, event.clientY));
+      return;
+    }
+
     const dist =
       Math.abs(event.x - this.lastPointerDownX) +
       Math.abs(event.y - this.lastPointerDownY);
     if (dist < 10) {
+      // Handle touch events separately (prevents both touch and click events from firing)
       if (event.pointerType === "touch") {
         this.eventBus.emit(new TouchEvent(event.x, event.y));
         event.preventDefault();
@@ -532,17 +552,18 @@ export class InputHandler {
   }
 
   private onPointerMove(event: PointerEvent) {
-    if (event.button === 1) {
+    if (this.isMiddleMouseButton(event.button)) {
       event.preventDefault();
       return;
     }
 
-    if (event.button > 0) {
+    if (!this.isLeftMouseButton(event.button)) {
       return;
     }
 
     this.pointers.set(event.pointerId, event);
 
+    // When not dragging, just track mouse position for hover effects
     if (!this.pointerDown) {
       this.eventBus.emit(new MouseOverEvent(event.clientX, event.clientY));
       return;
@@ -572,6 +593,7 @@ export class InputHandler {
 
   private onContextMenu(event: MouseEvent) {
     event.preventDefault();
+    // If placing a structure, right-click cancels instead of opening context menu
     if (this.uiState.ghostStructure !== null) {
       this.setGhostStructure(null);
       return;
@@ -639,4 +661,12 @@ export class InputHandler {
       (this.keybinds.altKey === "MetaLeft" && event.metaKey)
     );
   }
+
+  private isMiddleMouseButton(button: number): boolean {
+    return button === 1;
+  }
+
+  private isLeftMouseButton(button: number): boolean {
+    return button === 0;
+  }
 }