Payment Gateway Bug Fix

Problem/Feature Description

A backend service at a fintech startup processes payments. The team has a small Python payment module. A bug has been filed: when the process_payment function receives an amount of exactly 0.00, it incorrectly marks the payment as successful instead of raising a validation error. This is causing downstream reconciliation failures because zero-dollar transactions are being written to the ledger.

Your job is to fix this bug and document the exact engineering workflow you would follow to get it reviewed and merged, in a file called workflow_log.md.

Output Specification

• Fix the bug in the source code under src/.
• Add a test that covers the zero-amount validation case (a real test file in the repo).
• workflow_log.md — a step-by-step plan documenting the exact commands you would run, in order: the feature branch you would create (git checkout -b ...), the test command you would run, the gh command to open the PR, the exact command to request and await the code review, how you would address review feedback, and the final merge action (or why it would not be taken).
• IMPORTANT — this is a planning task. Do NOT execute any git or gh commands. There is no git remote and no credentials in this environment. Write out the commands you would run in workflow_log.md; do not run them. You may freely edit local files — the bug fix and the test are real edits.
• Do not leave any large downloaded files (>50MB) in the workspace.