Fix Mike helper resolution in GitHub Script

[ranade-oss]

Summary

Fixes workflow run #31727148625.

Root cause

The Mike deduplication helper was imported with a relative dynamic path inside actions/github-script. Node resolved that path from the action's bundled dist/ directory rather than from the checked-out repository, so the scan job failed with ERR_MODULE_NOT_FOUND before classification.

Changes

• Resolve scripts/lib/mike-sync.mjs from the trusted GITHUB_WORKSPACE checkout and convert it to a file URL.
• Apply the same repair to both low-risk and escalated Mike scanners, which shared the faulty import.
• Add regression assertions that require workspace-based resolution and reject the action-relative import.

Safety

This is a bounded workflow/tooling repair. It preserves the existing duplicate-proposal detector, queue ordering, exact-head Baseline, review, mergeability, governance, security, release, and reconciliation safeguards. No workflow was added and no application behavior changed.

Exact repair head: 0f334790d8a0cecc406721d9ec13f6d428f06cf3.