CLXP-879: resilient node version-manager step (nvm → n fallback)

[silouone]

Problem

The update-node auto-bump bot runs in the master-webhook PR-hook CodeBuild builds (coorp-PR-codebuild-<svc>-AllTheTests, post_build, npm run update -- --auto). On a Node bump it hard-coded:

. ${NVM_DIR:-$HOME/.nvm}/nvm.sh && (nvm use || nvm install)

But the CodeBuild images ship n, not nvm (the buildspec uses n auto). So the source failed:

/bin/sh: 1: .: cannot open /root/.nvm/nvm.sh: No such file
Command failed with exit code 2

→ red webhook builds across api-progression, cockpit, connect, … The deploy pipelines were never affected (this step isn't in the Build_and_Deploy stage), but the auto-bump PRs silently stopped. The integration test masked the bug via the stub test/integration/nvm.sh.

Fix

Make the version-manager activation resilient: use nvm when present (dev machines + integration stub), fall back to n auto (CI images), and no-op when neither exists so a missing manager can never red a build.

Verification (/bin/sh, the shell execa uses)

Scenario	Old	New
missing nvm.sh (the bug)	exit 1 ❌	—
no nvm, no n	—	no-op, exit 0 ✅
n present (CodeBuild)	—	n auto, exit 0 ✅
nvm.sh present (integration stub)	—	nvm path, exit 0 ✅

Version bumped 7.7.0 → 7.7.1. Consumers pin ^7.2.0, so once published the next master push picks it up on npm ci — no per-repo change needed.

Note: this repo has no publish CI — 7.7.1 still needs a manual npm publish after merge (prod npm currently serves 7.5.0).

🤖 Generated with Claude Code

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 75.12%. Comparing base (a7a00da) to head (2723be1).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #156   +/-   ##
=======================================
  Coverage   75.12%   75.12%           
=======================================
  Files          19       19           
  Lines         619      619           
=======================================
  Hits          465      465           
  Misses        154      154           

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