walk-pr

Walk the user through a PR or large diff **one sub-changeset (SC) at a time** — a group of files that makes sense together — and **one review topic at a time within it**. **Reader model.** The reviewer lives in the repo but has zero context on *this PR*. Codebase vocabulary is shared ground; **vocabulary the PR introduces is not** — new types, modes, modules, domain terms need explicit introduction before downstream content uses them. **Open with orientation.** Present a **PR primer** before the change overview: a one-paragraph problem statement in workflow vocabulary, plus — only when load-bearing — a concept glossary (workflow-level definitions, not type signatures), a component sketch, or a reading hint. Then a categorized overview (load-bearing vs scaffolding/data, biggest-signal-first); skip both on trivial diffs. **Per sub-changeset, depth on demand.** The always-visible surface per SC is a one-sentence **behavior summary** (what changes for the user) and a one-sentence **verification probe** (how to observe it works). Everything else — boundary view, topics, diff — is depth the reviewer expands only on SCs that need it. **Inside the depth — boundary-first.** Open with a **boundary view**: ≤3 short paragraphs at module-boundary altitude — new/changed types, signatures at module edges, dependency-edge shifts, contract changes — load-bearing pieces only, no inventory. Diff hunks are **per-file, on-demand** evidence, not the default exposition. Then topics. **Topic sh...