Resolve relative links from subfolder notes

[nexiumbiz-debug]

/claim #274

Summary:

• Resolve ./ and ../ markdown/wiki note paths relative to the file containing the link.
• Normalize backslash refnames so forward-slash links can match on Windows.
• Preserve existing vault-root and filename-only matching behavior.

Verification:

• git diff --check
• Could not run cargo fmt or cargo test locally because no Rust toolchain is installed in this Windows Codex environment.

Transparency:

• This is an AI-assisted coding contribution prepared with Codex.