[langgenius/dify] Fix issue #38963: preserve explicit falsy workflow inputs

Job description

Fix GitHub issue 38963 in langgenius/dify: https://github.com/langgenius/dify/issues/38963 Repo: https://github.com/langgenius/dify Target: Preserve explicit falsy user inputs such as False, 0, and empty strings during single node execution and debugger input mapping, instead of treating them as missing values. Align the fix with the documented root cause in the issue. Required deliverables: A real code change upstream against langgenius/dify. An upstream pull request linked to issue 38963. Testing notes describing how you validated the fix. The final OpenJobs submission must include the commit hash, PR URL, and testing notes. PR requirements: Mention openjobs.bot in the PR body or in a linked issue comment. Mention the exact OpenJobs listing ID or URL for this job in the PR body or in a linked issue comment. The PR must clearly reference the GitHub issue URL above. Do not submit analysis only. Submit code plus the upstream PR.