design(figma): error pattern kit for Stellar and StreamPay money-movement flows.

docs/error-pattern-kit.md

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+# Error Pattern Kit — Stellar & StreamPay Money-Movement Flows
+
+**Issue:** #47  
+**Status:** Design handoff — Figma kit pending attachment  
+**Scope:** UX/design only. No Next.js implementation in this PR.
+
+---
+
+## Error Archetypes
+
+| # | Archetype | `problem+json` code | Severity | Component |
+|---|-----------|---------------------|----------|-----------|
+| 1 | Insufficient balance | `op_underfunded` | High | Error/Inline |
+| 2 | Horizon / RPC outage | `horizon_unavailable` | Critical | Error/Blocking |
+| 3 | Transaction rejected on-chain | `tx_failed` | High | Error/Banner |
+| 4 | Wallet not connected | `wallet_disconnected` | Medium | Error/Inline |
+| 5 | Stream escrow below minimum | `escrow_below_minimum` | High | Error/Inline |
+| 6 | Network mismatch (testnet vs mainnet) | `network_mismatch` | Critical | Error/Blocking |
+
+---
+
+## Component Inventory
+
+- **Error/Inline** — field-level or card-level; no full stack trace; optional "Details" accordion for advanced mode
+- **Error/Banner** — page-level dismissible; includes request ID for support escalation
+- **Error/Blocking** — full-page or modal; blocks action until resolved
+
+## Suggested Next-Step Copy
+
+| Code | Primary CTA | Secondary |
+|------|-------------|-----------|
+| `op_underfunded` | Add funds | View balance |
+| `horizon_unavailable` | Try again | Check network status |
+| `tx_failed` | Retry transaction | Contact support (ref: `{requestId}`) |
+| `wallet_disconnected` | Connect wallet | — |
+| `escrow_below_minimum` | Adjust amount | Learn more |
+| `network_mismatch` | Switch network | — |
+
+## A11y Notes
+
+- Toasts: `role="alert"` + `aria-live="assertive"` for critical; `aria-live="polite"` for informational
+- Color is never the sole severity indicator — icon + label always accompany color
+- Grayscale print test required before v1 sign-off
+- WCAG AA contrast minimum; phase-2 gaps documented in Figma annotations
+
+## Handoff Checklist
+
+- [ ] Figma file linked to this issue
+- [ ] PDF export attached
+- [ ] Design crit completed (product + eng sign-off noted in Figma)
+- [ ] Named export assets listed in Figma handoff panel
+- [ ] Redlines and component specs present (no orphan screens)
+
+## Out of Scope
+
+Implementation in the Next.js app is tracked as a separate frontend issue.