refactor(guard): split baseline and metrics helpers

[eduardbar]

Summary

• Split guard baseline normalization into src/guard-baseline.ts.
• Split guard metric delta builders into src/guard-metrics.ts.
• Kept guard behavior intact while reducing structural hotspots in src/guard.ts.

Validation

• drift scan: totalScore 0, totalIssues 0
• tests: tests/phase1-init-doctor-guard.test.ts pass

[github-actions]

drift trust

drift trust

• Trust Score: 100/100
• Merge Risk: LOW
• Target: /home/runner/work/drift/drift

Diff signals

• Base ref: origin/master
• Diff status: IMPROVED
• Score delta: +0
• Issues: +0 new / -2 resolved
• Trust adjustment: +0 penalty / -4 bonus (net -4)

Top reasons

• none

Fix priorities

• none

drift review

drift review

ℹ️ No drift changes detected against base ref.

• Base ref: origin/master
• Score delta: +0
• New issues: 0
• Resolved issues: 2

File breakdown

• /home/runner/work/drift/drift/src/guard.ts: 35 -> 0 (-35), +0 new / -2 resolved