Testing/CI/tooling consistency (#9,#20,#21,#22,#23,#28) (#59)

Co-authored-by: claude <claude@jpaul.io>
Co-committed-by: claude <claude@jpaul.io>

modules/23-working-with-existing-codebases/README.md

@@ -170,8 +170,12 @@ This lab does **not** use `tasks-app` — the entire point is a codebase you *di
 - Git, Python 3.10+, and your agentic AI tool from Module 4.
 - A real, small-to-medium open-source repo to clone. Pick something with **tests** and a clear
   build/test command, in a language you can at least read. Good traits: a few thousand lines, an
-  obvious entry point, a green test suite. (Avoid giant frameworks for a first run — you want a
+  obvious entry point, a documented install (`pip install -e .`, `npm install`, `go mod download`,
+  …), and a test suite that **goes green on a clean clone after that documented install** — confirm
+  that before you rely on it as a baseline. (Avoid giant frameworks for a first run — you want a
   system you can't fully hold in your head, but whose test suite finishes in under a minute.)
+  **First time? Pick a small Python repo**, so the Module 13 testing toolchain you already have
+  transfers with the least friction.
 - The starter files from this module's `lab/` folder: `orient.py` and `skills/`.
 
 ### Part A — Clone and orient
@@ -205,9 +209,14 @@ This lab does **not** use `tasks-app` — the entire point is a codebase you *di
 ### Part C — One small, scoped, tested change
 
 6. Pick a genuinely small change — a clearer error message, a fixed edge case, a tiny missing
-   validation, a documented-but-unhandled input. Something a single function owns. Run the existing
-   tests first to establish a green baseline (`pytest`, `npm test`, `go test ./...` — whatever
-   `ORIENT.md` and the README confirmed).
+   validation, a documented-but-unhandled input. Something a single function owns. First **install
+   the project's dependencies** the way its README says — typically `pip install -e .` (Python),
+   `npm install` (JS/TS), `go mod download` (Go), or the equivalent — *then* run the existing tests
+   to establish a green baseline (`python -m unittest`, `pytest`, `npm test`, `go test ./...` —
+   whatever `ORIENT.md` and the README confirmed). A fresh clone usually won't run green until its
+   deps are installed; if it still won't go green on a clean clone *after* a documented install,
+   that's a setup problem, not your baseline — pick another repo rather than change code on top of an
+   environment you can't trust.
 
 7. Branch, then load the `safe-change` skill (`lab/skills/safe-change.md`) and work the change with
    the AI: