chore: script/bootstrap fails when node cannot find a module the tests load (closes #263)

yarn install exits 0 without touching node_modules whenever
node_modules/.yarn-integrity matches yarn.lock, so a package deleted from
node_modules stayed deleted while bootstrap printed "bootstrap complete".
After the install, bootstrap now asks node to resolve jest,
playwright-core and ethers, and on the first it cannot find it names the
module and the fix: rm -rf node_modules && make bootstrap.

Model: opus-5-5

README.md

@@ -218,7 +218,8 @@ development workflow, and the Makefile targets are thin shims that call them. We
 provide:
 
 - `script/bootstrap` — install all dependencies (pinned node via nvm if needed,
-  yarn via corepack, `yarn install --frozen-lockfile`)
+  yarn via corepack, `yarn install --frozen-lockfile`), then fail, naming the
+  module, if node cannot find `jest`, `playwright-core` or `ethers`
 - `script/setup` — make a fresh clone ready for development: bootstrap plus the
   git pre-commit hook
 - `script/projectname` — print the project name (used for the Docker image tag)