fix(ci): propagate exhausted npm install failures

[diegosouzapw]

Problem and change

When all three npm ci attempts fail, the composite action captures the status of
the completed if statement (zero). Downstream jobs then continue without installed
dependencies and the cache-miss path appears successful. Capture the npm exit in
the else branch so the final failed attempt fails the composite.

Validation

• RED on 06f1df9d775d: the actual Bash action returned 0 for 41,42,43 and 42,42,42.
• GREEN: 8/8 tests across the new behavioral fixture and existing cache-contract suite.
• Successful retry and initial success still stop immediately; retry delays remain 20/40s.
• Focused ESLint, Prettier, diff check and all pre-commit gates passed.

⚠️ base-red inherited: #13866. This PR repairs exit propagation only. Lockfile repair,
build fail-closed, the full quality profile and required verdict rollout are separate
items in the authorized recovery plan. Full release-green is not claimed here.