Fix: root prepare must not fail npm install in a build context

[vivek7405]

Summary

Hotfix for a production outage: all four Railway services (example-blog, website, docs, ui-website) fail to deploy. They build from the monorepo root, and the build dies at npm install:

[16/26] RUN npm install --no-audit --no-fund
Error: Cannot find module '/app/scripts/git-worktree-safe.mjs'
npm error command sh -c node scripts/git-worktree-safe.mjs
Build Failed

Root cause: #189 changed the root prepare to a bare node scripts/git-worktree-safe.mjs. In a Docker / Nixpacks build, npm install runs after COPY package.json but before the repo is fully copied, so scripts/ is not in the image yet. node exits 1 (module not found) and the build fails. The previous prepare ended in || true, so it never failed the install.

Fix

Restore the guard:

"prepare": "node scripts/git-worktree-safe.mjs 2>/dev/null || true"

A missing script (build context) or any git error is now a no-op that exits 0, so npm install never fails. The dev-machine self-heal still runs when the script is present.

Test plan

• New regression test runs the ACTUAL prepare command in a scriptless temp dir and asserts exit 0 (test/repo-health/prepare-build-safe.test.mjs).
• Counterfactual confirmed: the unguarded command exits 1 ("Cannot find module") in a scriptless dir, which is the exact build failure; the guarded command exits 0.
• Verified the script still heals + exits 0 when present (dev).

Definition of done

• Tests: Updated (new build-context regression test).
• Docs: N/A. One-line restoration of the prior resilient pattern; no surface change.
• Version bump: N/A. Root monorepo package.json (private, not published).

Expedited review given the live outage (one-line restoration of a known-good pattern with a proven counterfactual).