Delete the pre-generated starters/ directory tree (previously
synced from packages/ by generate-starters.ts). Add
extract-starter.ts which produces a starter tarball on demand
from any integration. Move shared starter template files to
showcase/shared/starter-template/.
audit.test.ts is 3034 lines / 119 tests and on Node 22 CI its single-file
runtime grew from 36.7s (PR #4071) to 71.4s (PR #4081) — over the hardcoded
60s birpc onTaskUpdate RPC window (vitest #6129). Same cliff that motivated
the validate-pins split earlier in this PR.
Extract makeTmpTree, makeConfig, writePackage, makeExampleDir, anomalyStrings,
and the AUDIT_SCRIPT path constant into audit.shared.ts so the forthcoming
split files can share them without duplication. No behavior change — the
original audit.test.ts still re-declares its own local copies until the
split commit removes them.