fix: strip shell comment lines before parsing claude_args

[VoidChecksum]

Summary

• The shell-quote library treats # as a shell comment character, causing all content after a # (including subsequent flags on new lines) to be silently swallowed
• Users adding documentation comments to their claude_args YAML inadvertently break flag parsing
• Fix: strip full comment lines (lines starting with #) before passing input to shell-quote

Before

claude_args: |
  --model 'claude-haiku-4-5'
  # This is a comment
  --allowed-tools 'mcp__github_inline_comment__create_inline_comment'

--allowed-tools is silently dropped — shell-quote puts it inside a comment object.

After

Comment lines are stripped before parsing, so both --model and --allowed-tools are correctly parsed. Inline # within quoted values (e.g., --prompt 'use color #ff0000') is preserved.

Changes

• base-action/src/parse-sdk-options.ts: Add stripShellComments() function, apply before parseShellArgs()
• base-action/test/parse-sdk-options.test.ts: Add 3 test cases covering comments, no comments, and inline # in values

Test plan

• Test: flags before and after comment line are both parsed
• Test: no-comment input still works
• Test: inline # in quoted values is NOT stripped
• Manual test with GitHub Actions workflow using comment-containing claude_args

Fixes #802

[Copilot]

Pull request overview

This PR fixes a parsing bug where shell-quote interprets # as a comment delimiter and can swallow subsequent flags in multiline claudeArgs. The fix preprocesses the argument string by removing full comment lines before invoking shell-quote, and adds tests to cover the behavior.

Changes:

• Add stripShellComments() to remove lines whose first non-whitespace character is # before parsing.
• Apply comment stripping in parseClaudeArgsToExtraArgs() prior to calling shell-quote.
• Add unit tests to verify flags around comment lines still parse and inline # in quoted values is preserved.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
base-action/src/parse-sdk-options.ts	Strips full-line # comments before shell-quote parsing to prevent later flags from being swallowed.
base-action/test/parse-sdk-options.test.ts	Adds regression tests for comment-line stripping and preserving inline # inside quoted values.

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