Linear walkthrough

Explain how the code in scope actually runs, in order, so the reader understands it without reading every file. The walkthrough is a reading aid, not a review: describe what the code does and why, and flag risks you notice, but do not change code.

1. Settle the scope

Resolve the target from the request:

• A change: uncommitted work (git diff, git diff --cached), a commit (git show <rev>), a range (git diff <base>..<head>), or a branch against its base (git diff <base>...<branch>).
• A feature or flow: start from its entry point (route, command, event handler, exported function) and follow the calls.
• A module or codebase: start from its public entry points.

Resolve an unnamed target from the conversation. Use the working changes or last commit only when the request points there. Ask once when ambiguity would produce different walkthroughs.