Replace legacy demos with the 200ms demo

.github/workflows/test-200ms-demo.yml

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+name: 200ms demo
+
+on:
+  pull_request:
+    paths:
+      - "200ms-demo/**"
+      - ".github/workflows/test-200ms-demo.yml"
+  push:
+    branches: [master]
+    paths:
+      - "200ms-demo/**"
+      - ".github/workflows/test-200ms-demo.yml"
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: 200ms-demo
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v6
+
+      - name: Set up Node
+        uses: actions/setup-node@v6
+        with:
+          node-version: 22
+          cache: npm
+          cache-dependency-path: 200ms-demo/package-lock.json
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Test exact rate math
+        run: npm run test:math
+
+      - name: Build the hosted path
+        run: npm run build:pages

200ms-demo/.gitignore

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+node_modules
+dist
+.DS_Store
+*.local
+npm-debug.log*

200ms-demo/PHASE1.md

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+# Phase 1 live-chain report
+
+Verified against Base Vibenet on September 10, 2026.
+
+## Final passing configuration
+
+- Chain ID: `84538453`
+- Sender implementation: `CanonicalHighRatePayerAccount`
+  (`0x813002ffdd25c81cef79781702176d453af0fa57` at test time)
+- Bootstrap transaction: ordered nonce key `0`
+- Streaming transactions: nonce-free `nonceKeyMax`, 15-second validity
+- Cadence: self-correcting 200ms schedule
+- Gas limit: sequenced estimate + nonce-free surcharge + 30% headroom
+- Receipt reconciliation: independent watcher with exact signed-byte rebroadcast
+
+## 50-transfer gate
+
+| Metric | Result |
+| --- | ---: |
+| Transfers | 50 |
+| Recipient delta | 0.833300 USDV |
+| Broadcast duration | 9.922s |
+| Accepted throughput | 5.04 tx/s |
+| Confirmation duration | 10.824s |
+| Confirmed throughput | 4.62 tx/s |
+| Mean gas per transfer | 50,017 |
+| Sampled base fee | 1 gwei |
+| Cost per transfer | 0.000050017 ETH |
+| 0.1 ETH runway | 1,999 transfers |
+| Runway at 5 tx/s | 6.66 minutes |
+
+## Five-minute streamer/funding soak
+
+The corrected hot loop then ran for five minutes with `npm run soak`:
+
+| Metric | Result |
+| --- | ---: |
+| Transfers | 1,500 |
+| Recipient delta | 24.999000 USDV |
+| Broadcast duration | 299.915s |
+| Accepted throughput | 5.00 tx/s |
+| Confirmation duration | 303.017s |
+| Confirmed throughput | 4.95 tx/s |
+| Mean gas per transfer | 50,040 |
+| Automatic ETH top-ups | 1 |
+
+Two absent transactions were recovered by exact signed-byte rebroadcast during
+the soak. There were no unrecovered nonce failures, and every transfer was
+included in the final authoritative recipient balance delta.
+
+## Rejected designs discovered by the gate
+
+1. **Unchecked ordered-nonce bursts:** a lower sequence could disappear after
+   the RPC returned its hash. Later sequences then filled the sender signature
+   pool and produced `sender EIP-8130 signature limit reached`.
+2. **Receipt work inside the queue:** throughput fell to 2.65 tx/s.
+3. **Visibility acknowledgement through the account RPC proxy:** consistent but
+   effectively receipt-paced at 1.39 tx/s.
+4. **Account configuration lock:** the current execution client rejected the
+   lock change as `unknown account-change op in the enshrined apply path`.
+5. **60-second nonce-free validity:** the live admission window is 20 seconds;
+   the working path uses 15 seconds.
+
+Run the gate again with:
+
+```bash
+npm run spike
+```

200ms-demo/README.md

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+# 200ms demo
+
+A single-page React app that streams Vibenet USDV through real EIP-8130 native
+account-abstraction transactions at approximately five transfers per second.
+It uses a locally generated devnet key: no wallet connection, extension, or
+signing prompt.
+
+Live preview: <https://youssefea.github.io/demos/200ms/>
+
+The workflow committed to `base/demos` validates this directory but does not
+deploy to the Base organization GitHub Pages site.
+
+## Run
+
+```bash
+npm install
+npm run dev
+```
+
+Open the printed local Vite URL. A fresh browser profile takes roughly 12–20
+seconds to receive both faucet drips because Vibenet enforces a shared ten-second
+IP cooldown.
+
+## Verify the live transaction path
+
+```bash
+npm run spike
+```
+
+The spike creates a disposable high-rate account, funds it, deploys it, and
+sends 50 real USDV transfers. See [PHASE1.md](./PHASE1.md) for the passing
+September 10, 2026 measurements and the designs rejected during testing.
+
+The five-minute funding/throughput soak is available as `npm run soak`.
+
+## Architecture
+
+- `src/chain/bootstrap.ts` — health, live contracts, persisted account,
+  cooldown-aware funding, deployment proof, and one-time gas calibration.
+- `src/chain/streamer.ts` — exact rational accumulator, 200ms scheduler,
+  nonce-free signing, pending backpressure, receipt watcher, rebroadcast,
+  funding daemon, and reset detection.
+- `src/hooks/useStream.ts` — requestAnimationFrame sampling over the mutable
+  streamer snapshot.
+- `src/ui/` — counter, real balance cards, rate selector, and explorer-linked
+  transaction ticker.
+
+## Important limitations
+
+- **Devnet only.** The private signing key is stored in localStorage. Do not
+  point this storage model at production assets.
+- **USDV, not USDC.** USDV is Vibenet's faucet-backed six-decimal test USD token.
+- The high-rate account implementation restricts outbound ETH execution. The
+  app only calls the USDV token and uses ETH for transaction fees.
+- There is no mock fallback. If Vibenet is down, the app says so.
+- Browsers call Vibenet directly. Visitors behind the same NAT or corporate
+  egress can still contend for the faucet's IP cooldown.

200ms-demo/index.html

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+<!doctype html>
+<html lang="en">
+  <head>
+    <meta charset="UTF-8" />
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <meta name="theme-color" content="#ffffff" />
+    <meta name="description" content="The 200ms demo streams USDV through real EIP-8130 transfers at block cadence." />
+    <title>200ms demo</title>
+  </head>
+  <body>
+    <div id="root"></div>
+    <script type="module" src="/src/main.tsx"></script>
+  </body>
+</html>