fix: wait for npm install readiness

[sdsrss]

Summary

• treat npm pack plus isolated npm install --ignore-scripts as one registry-readiness retry attempt
• clean each failed attempt temporary prefix and newly created tarball without touching pre-existing destination contents
• publish the synchronized v5.0.1 patch after the v5.0.0 release exposed the multi-endpoint propagation race

Validation

• RED regression: old helper returned success after attempt 1 while install metadata remained unavailable
• node --test scripts/tests/release-registry-pack.test.js — 11/11 passed
• real temporary npm pack/install probe against @sdsrs/agentsmd@5.0.0
• npm run check — complete Node/Bash suite, hook smoke 382/382, ShellCheck clean, live guard 24 surfaces unchanged
• packed @sdsrs/agentsmd@5.0.1: 112 entries, forbidden release paths 0
• staged secrets gate and git diff --cached --check passed

Rollback

Revert commit 14c04691026cba6952981313b632ba4eedf2aa5a or remain on immutable v5.0.0.