fix(ui): claude mcp add takes URL as positional arg, not --url

The generated Claude Code snippet was outputting:
  claude mcp add ... scribe-dev --url <URL> --header ...

But `claude mcp add` errors out with `unknown option '--url'`. The
URL is a positional argument, not a flag:
  claude mcp add [--transport ...] [--scope ...] <name> <url> [--header ...]

Dropped --url and put the URL inline as a positional. Claude Desktop
JSON snippet was already correct (uses {url, headers} keys, not a
CLI flag).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/src/views/SettingsView.vue

@@ -143,8 +143,10 @@ const effectiveMcpName = computed(() => (mcpServerName.value || '').trim() || _D
 const effectiveApiKey = computed(() => newKeyValue.value || '<your-token>');
 
 const claudeCodeCommand = computed(() => {
+  // Note: `claude mcp add` takes the URL as a positional arg, not --url.
+  // Layout: claude mcp add [--transport ...] [--scope ...] <name> <url> [--header ...]
   return `claude mcp add --transport http --scope ${mcpScope.value} ${effectiveMcpName.value} \\
-  --url ${mcpUrl.value} \\
+  ${mcpUrl.value} \\
   --header "Authorization: Bearer ${effectiveApiKey.value}"`;
 });