examples: migrate to the native data layer (drop ws/coder-websocket/jackson/jsonlite) (#316)

Stacked on #315 (the native Binance REST fetcher). Retarget to `main` once #315 merges.

Migrates the runnable examples off third-party data-I/O packages onto Wickra's
native data layer (`CandleReader`, `Resampler`, `BinanceFeed`, `fetch_*klines`).

## Third-party packages removed (the zero-dep selling point)
- **Node**: `ws` (live feed → BinanceFeed) — dropped from package.json + lockfile
- **Go**: `github.com/coder/websocket` — dropped from go.mod / go.sum (`go mod tidy`)
- **Java**: `jackson-databind` (live feed + REST fetch) — dropped from pom.xml
- **R**: `jsonlite` + `websocket` + `later` — dropped from the README notes

Each language's CSV loading now goes through `CandleReader`, manual resampling
through `Resampler`, the live feed through `BinanceFeed`, and (Java/R) the REST
download through the native fetcher.

## Verification
Ran the offline examples per language against the bundled data — backtest and
multi_timeframe produce identical output across Python / Node / Go / Java / R
(e.g. ATR(14) last 345.1010; 1h→5m resamples to 240 bars, →15m to 80 bars).

C# / C / WASM (stdlib-only, no third-party deps to remove) follow in this branch.

Note: the streaming `strategy_*` examples have pre-existing candle-indicator
runtime bugs (CI only syntax-smokes them); the CSV migration preserves their
shape and leaves those bugs for a separate fix.

examples/wasm/strategy_macd_adx.html

@@ -47,33 +47,24 @@
   </p>
 
   <script type="module">
-    import init, { version, installPanicHook, MACD, ADX } from "../../bindings/wasm/pkg/wickra_wasm.js";
+    import init, {
+      CandleReader, version, installPanicHook, MACD, ADX } from "../../bindings/wasm/pkg/wickra_wasm.js";
 
     const FEE = 0.001;
     const ADX_FLOOR = 20.0;
-    const REQUIRED = ["timestamp", "open", "high", "low", "close", "volume"];
 
     function parseCsv(text) {
-      const lines = text.split(/\r?\n/).filter((line) => line.length > 0);
-      if (lines.length === 0) throw new Error("file is empty");
-      const header = lines[0].split(",").map((s) => s.trim());
-      const missing = REQUIRED.filter((c) => !header.includes(c));
-      if (missing.length > 0) {
-        throw new Error(`missing required column(s): ${missing.join(", ")}; found: ${header.join(", ")}`);
-      }
-      if (lines.length === 1) throw new Error("CSV has a header but no data rows");
-      const idx = {};
-      for (const c of REQUIRED) idx[c] = header.indexOf(c);
-      const cols = { open: [], high: [], low: [], close: [], volume: [] };
-      for (let i = 1; i < lines.length; i++) {
-        const cells = lines[i].split(",");
-        for (const c of ["open", "high", "low", "close", "volume"]) {
-          const v = Number(cells[idx[c]]);
-          if (!Number.isFinite(v)) {
-            throw new Error(`row ${i + 1} column '${c}' is not numeric: ${JSON.stringify(cells[idx[c]])}`);
-          }
-          cols[c].push(v);
-        }
+      // Native CandleReader: header validation, BOM/whitespace tolerance. No
+      // manual CSV parsing.
+      const candles = new CandleReader(text).read();
+      const cols = { timestamp: [], open: [], high: [], low: [], close: [], volume: [] };
+      for (const c of candles) {
+        cols.timestamp.push(c.timestamp);
+        cols.open.push(c.open);
+        cols.high.push(c.high);
+        cols.low.push(c.low);
+        cols.close.push(c.close);
+        cols.volume.push(c.volume);
       }
       return cols;
     }