feat: Ensure ClaudeCodeAdd correctly escapes file path argument

[HsiuCL]

Summary

Fix ClaudeCodeAdd command to correctly handle file paths containing spaces by adding a backslash-escape-aware argument parser. Previously, vim.split(args, "%s+") would incorrectly split escaped paths like file\ name.lua into separate tokens, breaking file resolution and potentially misinterpreting path fragments as line numbers.

Changes

Escaped argument parser

• Added parse_escaped_args() function that respects backslash-escaped spaces (\ ) and escaped backslashes (\\) when splitting command-line arguments
• Replaced vim.split(opts.args, "%s+") with parse_escaped_args(opts.args) in the ClaudeCodeAdd command handler
• Unescaped whitespace is treated as a delimiter; \ is preserved as a literal space within a token

Test coverage

• Added 5 new tests under an "escaped path handling" describe block:
  • Backslash-escaped spaces in file paths are correctly parsed
  • Escaped spaces are not confused with argument delimiters (e.g., file\ 1 is treated as a path, not path + line number)
  • Escaped paths work correctly with line range arguments
  • Escaped paths work correctly with a start-line-only argument
  • Non-escaped paths continue to work as before

Notable Details

• The parser is intentionally minimal — it only handles \ (escaped space) and \\ (escaped backslash). Other escape sequences pass the backslash through unchanged, matching shell-like conventions.
• No breaking changes: paths without spaces behave identically to the previous implementation.