Fix console escaping of placeholder values

[theletterf]

Fixes #2007

Claude's diagnosis:

When you use console syntax highlighting, the text fragments like don't render because:

1. Console blocks use a different rendering path: In Code.cshtml (lines 12-21), console blocks render through ApiSegments using RenderLineWithCallouts() instead of the standard RenderCodeBlockLines() method.
2. No HTML escaping in console rendering: The RenderLineWithCallouts() method in CodeViewModel.cs (lines 33-62) directly appends the content to the HTML string without escaping HTML entities (line 53):
   _ = html.Append(line); // No HTML escaping!
3. Standard code blocks ARE escaped: When using any other language, the rendering goes through EnhancedCodeBlockHtmlRenderer.RenderCodeBlockLines() which calls renderer.WriteEscape(slice) (line 61), properly
   escaping HTML entities like < and >.

So when you write in a console block, the browser interprets it as an HTML tag (which doesn't exist), so it doesn't render. In other languages, it gets escaped to <password> and displays
correctly.

Which makes sense if Console blocks were created differently or before we had callouts

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Authored using Claude 4.5 in Claude CLI 2.0 with some human intervention

[github-actions]

🔍 Preview links for changed docs

• docs/syntax/code.md

[theletterf]

@shainaraskas Check it out! :) https://docs-v3-preview.elastic.dev/elastic/docs-builder/pull/2029/syntax/code#console-code-blocks