feat(skills): Add stripe-best-practices from Anthropic official

- Source: anthropics/claude-plugins-official
- Modern API guidance (CheckoutSessions over Charges)
- Frontend integration priorities
- Subscription/billing best practices
- Added Firefrost/Arbiter context
- Updated SKILLS-INDEX.md

Chronicler #73

docs/skills/SKILLS-INDEX.md

@@ -169,6 +169,28 @@
 
 ---
 
+### stripe-best-practices
+**Location:** `docs/skills/stripe-best-practices/SKILL.md`  
+**Source:** skill.fish (anthropics/claude-plugins-official)  
+**Triggers:** Stripe, payments, checkout, subscriptions, webhooks, billing, Arbiter payments
+
+**Purpose:** Official Anthropic guidance for Stripe integrations
+
+**What It Covers:**
+- Modern vs deprecated APIs (CheckoutSessions vs Charges)
+- Frontend integration priority (hosted checkout preferred)
+- Subscription/billing best practices
+- Connect platform guidance
+- Dynamic payment methods
+
+**Read This When:**
+- Reviewing Arbiter's Stripe integration
+- Working on Task #87 (lifecycle handlers)
+- Implementing new payment features
+- Troubleshooting webhook issues
+
+---
+
 ### postgres-patterns
 **Location:** `docs/skills/postgres-patterns/SKILL.md`  
 **Source:** skill.fish (affaan-m/everything-claude-code)  
@@ -329,6 +351,8 @@ docs/skills/
 │   └── SKILL.md
 ├── postgres-patterns/
 │   └── SKILL.md
+├── stripe-best-practices/
+│   └── SKILL.md
 └── discord-automation/          (skill collection)
     ├── README.md
     ├── discord-create-channel.md

docs/skills/stripe-best-practices/SKILL.md

@@ -0,0 +1,129 @@
+---
+name: stripe-best-practices
+description: |
+  Best practices for building Stripe integrations. Use when implementing 
+  payment processing, checkout flows, subscriptions, webhooks, or any 
+  Stripe API integration. Reference for Arbiter's payment system.
+source: skill.fish (anthropics/claude-plugins-official)
+---
+
+# Stripe Integration Best Practices
+
+Official Anthropic guidance for Stripe integrations.
+
+---
+
+## WHEN TO USE
+
+- Implementing payment processing
+- Building checkout flows
+- Setting up subscriptions
+- Handling webhooks
+- Reviewing Arbiter's Stripe integration
+- Task #87 (lifecycle handlers)
+
+---
+
+## KEY PRINCIPLES
+
+### Always Use Modern APIs
+
+| ✅ Use | ❌ Never Use |
+|--------|-------------|
+| CheckoutSessions | Charges API |
+| PaymentIntents | Sources API |
+| SetupIntents | Legacy Card Element |
+| Payment Element | Tokens (unless necessary) |
+
+### API Priority
+
+1. **CheckoutSessions** — Primary for on-session payments (one-time + subscriptions)
+2. **PaymentIntents** — For off-session payments or custom checkout state
+3. **SetupIntents** — For saving payment methods for later
+
+### Frontend Priority
+
+1. **Stripe-hosted Checkout** — Preferred (what Arbiter uses)
+2. **Embedded Checkout** — Good alternative
+3. **Payment Element** — Only if advanced customization needed
+
+---
+
+## SUBSCRIPTIONS & BILLING
+
+For recurring revenue (like Firefrost subscriptions):
+- Use **Billing APIs** to plan integration
+- Combine with **Stripe Checkout** for frontend
+- Follow [Subscription Use Cases](https://stripe.com/docs/billing/subscriptions/overview)
+
+---
+
+## BEST PRACTICES
+
+### Dynamic Payment Methods
+Turn on in dashboard settings instead of passing specific `payment_method_types`. Stripe auto-selects based on user location, wallets, and preferences.
+
+### Saving Payment Methods
+Use **SetupIntent API** — never Sources API.
+
+### Before Confirming Payment
+If you need to inspect card details before payment (e.g., surcharging), use **Stripe Confirmation Tokens** — not `createPaymentMethod` or `createToken`.
+
+### PCI Compliance
+Server-side raw PAN data requires proving PCI compliance. Point users migrating from other processors to Stripe's migration process.
+
+---
+
+## CONNECT PLATFORMS
+
+If building a platform with fund flows:
+
+| Charge Type | When to Use |
+|-------------|-------------|
+| **Direct charges** | Stripe takes risk |
+| **Destination charges** | Platform accepts liability |
+
+- Use `on_behalf_of` parameter to control merchant of record
+- Never mix charge types
+- Use controller properties (not outdated Standard/Express/Custom terms)
+
+---
+
+## IMPORTANT LINKS
+
+- [Integration Options](https://stripe.com/docs/payments/online-payments)
+- [API Tour](https://stripe.com/docs/api)
+- [Go Live Checklist](https://stripe.com/docs/development/checklist)
+- [Subscription Use Cases](https://stripe.com/docs/billing/subscriptions/overview)
+
+---
+
+## FIREFROST CONTEXT
+
+**Arbiter's Current Implementation:**
+- ✅ Uses Stripe Checkout (hosted) — correct approach
+- ✅ Uses webhooks for subscription events
+- Stripe keys in `.env` on Command Center
+
+**Task #87 (Lifecycle Handlers):**
+- Cancellation handling
+- Grace period management  
+- Chargeback processing
+- Should follow these best practices
+
+**Subscription Tiers:**
+| Tier | Price | Type |
+|------|-------|------|
+| Awakened | $1 | One-time |
+| Elemental | $5/mo | Monthly |
+| Knight | $10/mo | Monthly |
+| Master | $15/mo | Monthly |
+| Legend | $20/mo | Monthly |
+| Sovereign | $50 | One-time |
+
+---
+
+**Source:** skill.fish — anthropics/claude-plugins-official  
+**Added:** 2026-04-09 by Chronicler #73
+
+**Fire + Frost + Foundation = Where Love Builds Legacy** 💙🔥❄️