Add Remotion explainer video for the write flow

video/.gitignore

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+node_modules
+out
+.DS_Store
+*.local

video/README.md

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+# SuiOptions — Write-Flow Explainer Video
+
+A [Remotion](https://www.remotion.dev/) project that animates the **write flow**
+of the SuiOptions covered-call protocol: how a retail writer sells a covered call
+to a market maker, from RFQ to on-chain fill, ending with the protocol's
+pooled-bucket / FIFO-cursor settlement model.
+
+Source of truth for the content: [`../options-protocol-spec.md`](../options-protocol-spec.md).
+
+## Output
+
+- Composition id: `WriteFlowExplainer`
+- 1920×1080, 30 fps, ~52 s (1575 frames)
+- Rendered to `out/write-flow.mp4`
+
+## Scenes
+
+| # | Scene | What it shows |
+|---|-------|---------------|
+| 00 | Title | Intro to the write flow |
+| 01 | The cast | Writer · Quoting Service · Trader MMs · Sui contracts (§1.2) |
+| 02 | Request for quote | `RFQRequest` → service fans out `RFQBroadcast` to MMs (§5.8) |
+| 03 | Quotes & reservation | MMs return signed quotes; service validates, reserves, sorts (§5.4, §5.5) |
+| 04 | The fill | `execute_write` verifies, skims fee, pays premium, mints Position + CallOption (§3.3.4) |
+| 05 | The cursor model | Shared bucket, FIFO `exercise_cursor`, redeem math (§2.2) |
+| 06 | Recap | The four steps end to end |
+
+## Develop
+
+```bash
+npm install
+npm run dev      # opens Remotion Studio (live preview / scrubbing)
+```
+
+## Render
+
+```bash
+npm run render   # -> out/write-flow.mp4
+# equivalent: npx remotion render src/index.ts WriteFlowExplainer out/write-flow.mp4
+```
+
+## Structure
+
+```
+src/
+├── index.ts            registerRoot
+├── Root.tsx            <Composition> registration
+├── ExplainerVideo.tsx  scene timeline (Series)
+├── theme.ts            colors / fonts
+├── layout.ts           shared actor positions
+├── anim.ts             spring/fade helpers
+├── components/         Background, Actor, MessagePacket, Wire, Caption
+└── scenes/             one file per scene
+```