[AUDIT-012] Document Workflow DevKit undici override chain

[groupthinking]

[AUDIT-012] Workflow DevKit Override Chain Not Documented (🟡 MEDIUM)

Title: Document Workflow DevKit undici override chain

Description:
package.json contains extensive overrides for Workflow DevKit compatibility:

"@workflow/world-local": { "undici": "^7.29.0" },
"@workflow/world-vercel": { "undici": "^7.29.0" }

This is not documented anywhere, causing confusion during:

• Dependency upgrades
• Debugging fetch issues
• Onboarding new developers

Impact: Dependency resolution confusion, deployment debugging friction, upgrade uncertainty

Files to Review:

• package.json:22-51 (overrides block)
• apps/web/next.config.js:10-17 (withWorkflow)
• Architecture docs

Required Actions:

1. Document why overrides are needed
2. Add comments to package.json explaining each override
3. Create upgrade guide for Workflow DevKit
4. Document fetch/undici version constraints

Acceptance Criteria:

• Each override documented with reason
• Workflow DevKit integration guide created
• Upgrade path documented
• Comments added to package.json

Labels: 🟡 medium, documentation, dependencies, frontend

Related: .github/AUDIT_FINDINGS_SESSION.md Section 12

---

Audit master doc: .github/AUDIT_FINDINGS_SESSION.md
Source session: https://github.com/groupthinking/EventRelay/tasks/36f6c3e5-60dc-4dfe-a151-ef2ab9114afa
Remediation phase: Phase 4: Operational (Ongoing)

Cross-links: Previous: #2173 | Audit index: #2163

[linear-code]

GRV-670

[github-actions]

👋 Thanks for opening this issue! It has been automatically labeled for triage.

[groupthinking]

Tracker: #2175