[Bug] Generating PHPDoc annotations for PHP functions fails with `E5108: snippet parsing failed`

[Alexandros-Pallis]

Description

Generating PHPDoc annotations for PHP functions fails with E5108: snippet parsing failed when using the nvim snippet engine.

Steps to Reproduce

1. Configure neogen with snippet_engine = "nvim"
2. Create a PHP function:

function test($data, $message) {
    return $data;
}

3. Run :Neogen on the function
4. Error: E5108: Error executing lua: .../vim/lsp/_snippet_grammar.lua:178: snippet parsing failed

Expected Behavior

PHPDoc comment should be generated successfully.

Actual Behavior

Snippet parsing fails because neogen generates invalid LSP snippet syntax:

Root Cause

Commit aeea21f added $$ escaping for PHP variables, but:

• LSP snippet spec requires \$ for literal dollar signs (not $$)
• The nvim and mini engines use LSP spec
• LuaSnip and others use $$ escaping

The current implementation escapes ALL $ to $$, which is incompatible with LSP-compliant engines.

Environment

• Neogen: d7f9461 (latest)
• Neovim: v0.11.5
• Snippet engine: nvim
• Language: PHP

References

• LSP snippet spec: https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#snippet_syntax
• Related to PHP - No starting dollar for function parameters #207