RM-01: reproducible checkout — the pre-push gate fails on code, not environment (#1027)

Co-authored-by: mos-dt-0 <[email protected]>

README.md

@@ -201,8 +201,21 @@ git clone [email protected]:mosaicstack/stack.git
 cd stack
 
 # Install dependencies. The local tier uses in-process PGlite; leave DATABASE_URL unset.
+# The pnpm store defaults to $HOME/.local/share/pnpm/store. Override it without
+# editing the checkout with NPM_CONFIG_STORE_DIR=$HOME/another-store if needed.
 pnpm install
 
+# Verify dependencies and generated state before running source-quality gates.
+# Missing dependencies exit 42; stale/foreign apps/web/.next state exits 43.
+# The web build certifies its exact standalone symlink manifest; added, removed,
+# retargeted, or manifest-only-tampered generated links also exit 43. This detects
+# accidental, independent, stale, and foreign-residue mutation—the class exposed by
+# a five-month-stale .next that produced 19 phantom TS2307 errors.
+# It does NOT defend against a same-UID actor that can rewrite both manifest and
+# marker consistently (CWE-345). RM-59 tracks the required executor/spine-side
+# trust anchor outside worktree authority.
+pnpm preflight
+
 # Optional local queue service only. This does not start PostgreSQL.
 docker compose up -d valkey
 
@@ -230,6 +243,7 @@ Gateway start command until KBN-101-02 makes that state fail closed.
 ### Quality Gates
 
 ```bash
+pnpm preflight               # Checkout/dependency/generated-state validation
 pnpm typecheck               # TypeScript type checking (all packages)
 pnpm lint                    # ESLint (all packages)
 pnpm test                    # Vitest (all packages)