fix: strip shell comments from claude_args before parsing

[AlexanderBartash]

Summary

• Fixes shell-quote library treating # as comment character, which swallows all subsequent content (including flags on new lines)
• Adds stripShellComments() function to remove shell-style comment lines before parsing

Problem

The shell-quote library treats # as a shell comment character. When users include comments in their claude_args:

claude_args: |
  --model 'claude-haiku'
  # This is a comment
  --allowed-tools 'mcp__github_inline_comment__*'

Everything after # is swallowed into a comment object, causing --allowed-tools to be lost.

Evidence:

parseShellArgs("--model 'haiku'\n# Comment\n--allowed-tools 'Edit'")
// Returns: ["--model", "haiku", { comment: " Comment\n--allowed-tools 'Edit'" }]
//                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
//                               The flag is INSIDE the comment!

Solution

Strip shell-style comment lines (lines starting with optional whitespace + #) before passing to shell-quote:

function stripShellComments(input: string): string {
  return input
    .split("\n")
    .filter((line) => !line.trim().startsWith("#"))
    .join("\n");
}

Test plan

• Added 6 new tests for shell comment handling
• All 27 tests in parse-sdk-options.test.ts pass
• Tests cover: basic comments, multiline comments, comments with quoted strings, comments with flag-like text, indented comments, hash characters inside quotes

Fixes #802