fix: render correct meta key in keyboard hints on Windows/Linux

Hardcoded ⌘ glyphs in compose hints were misleading on non-mac
platforms. Add a tiny platform helper sourced from the existing
window.electronWindow.platform bridge and substitute "Ctrl" off mac.
Closes #167.

https://claude.ai/code/session_01YZY4wUqACT7mgibHr2Yncx

js/src/features/compose/configure-stream-step.tsx

@@ -1,6 +1,7 @@
 import { useState, useCallback } from "react";
 import { useNetworks } from "@/hooks/use-networks";
 import { cn, removeDuplicates } from "@/lib/utils";
+import { metaKey } from "@/lib/platform";
 import { useAuthStore } from "@/stores/auth-store";
 import { generateRandomName } from "@/lib/random-name";
 import { Input } from "@/components/ui/input";
@@ -163,7 +164,7 @@ export function ConfigureStreamStep({
         </span>
         <span>
           <kbd className="rounded bg-white/10 px-1.5 py-0.5 font-mono text-xs">
-            ⌘+Enter
+            {metaKey}+Enter
           </kbd>{" "}
           create
         </span>

js/src/features/compose/text-editor.tsx

@@ -1,6 +1,7 @@
 import { useEffect, useRef, useCallback, useState } from "react";
 import { Paperclip } from "lucide-react";
 import { cn } from "@/lib/utils";
+import { metaKey } from "@/lib/platform";
 import { useAllLinkMetadata } from "@/hooks/use-link-metadata";
 import { AttachmentStrip } from "@/features/compose/attachment-strip";
 import type { PendingAttachment } from "@/features/compose/attachment-strip";
@@ -178,14 +179,14 @@ export function TextEditor({
       </span>
       <span>
         <kbd className="rounded bg-white/10 px-1.5 py-0.5 font-mono text-xs">
-          ⌘+Enter
+          {metaKey}+Enter
         </kbd>{" "}
         {submitHint}
       </span>
       {immersive && (
         <span>
           <kbd className="rounded bg-white/10 px-1.5 py-0.5 font-mono text-xs">
-            ⌘+M
+            {metaKey}+M
           </kbd>{" "}
           markdown
         </span>

js/src/lib/platform.ts

@@ -0,0 +1,5 @@
+export const isMac = window.electronWindow?.platform === "darwin";
+
+// Symbol to show in keyboard hints for the primary modifier
+// (Cmd on macOS, Ctrl on Windows/Linux).
+export const metaKey = isMac ? "⌘" : "Ctrl";