fix(llm): trim trailing blank lines from the markdown output

[markdumay]

Problem

safe-content.html trims only leading newlines (strings.TrimLeft "\n"). Content with trailing blank lines therefore leaves stray blank lines at the end of the generated index.md / llms.txt, which markdownlint flags as MD012 (multiple consecutive blank lines).

This shows up with generated / content-adapter pages and multi-shortcode output — e.g. a JSON-Schema table renderer that emits one {{< schema >}} call per definition: each call's trailing newline plus the join newline accumulate into trailing blanks the wrapper preserves.

Fix

Trim both ends and emit a single final newline:

- {{- $content = strings.TrimLeft "\n" $content -}}
- {{- return $content -}}
+ {{- $content = strings.Trim $content "\n" -}}
+ {{- return (printf "%s\n" $content) -}}

Result: no trailing blank lines (MD012) and a single final newline (MD047). The leading trim is preserved (the caller still controls top-of-content spacing).

Verification

Added exampleSite/content/docs/trailing-blanks.md (a page with trailing blank lines). Before: its index.md ended with …\n\n → MD012. After: ends with a single \n, MD012/MD047 clean. No change to existing pages (getting-started, blog, etc. still end with a single newline).

🤖 Generated with Claude Code

[markdumay]

🎉 This PR is included in version 1.3.4 🎉

The release is available on GitHub release

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