feat: improve text/binary file detection in hash.js (#17543)

* Improve text/binary file detection in hash.js

Replace hardcoded text: true with proper detection logic that:
- Checks for null bytes to identify binary files
- Validates UTF-8 encoding with round-trip verification
- Handles binary files by encoding them as base64

This fixes the TODO comment and makes the script more robust.

* tweak

* snake_case

---------

Co-authored-by: Gittensor Miner <miner@gittensor.io>
Co-authored-by: Rich Harris <rich.harris@vercel.com>

playgrounds/sandbox/scripts/hash.js

@@ -1,16 +1,44 @@
 import fs from 'node:fs';
 
+/**
+ * Detects if a file is text or binary by checking for null bytes
+ * and validating UTF-8 encoding
+ * @param {string} filepath - Path to the file
+ * @returns {boolean} - true if file is text, false if binary
+ */
+function is_text_file(filepath) {
+	const buffer = fs.readFileSync(filepath);
+	// Check for null bytes which indicate binary files
+	for (let i = 0; i < buffer.length; i++) {
+		if (buffer[i] === 0) {
+			return false;
+		}
+	}
+	// Validate UTF-8 encoding
+	try {
+		const text = buffer.toString('utf-8');
+		// Verify round-trip encoding to ensure valid UTF-8
+		const encoded = Buffer.from(text, 'utf-8');
+		return buffer.equals(encoded);
+	} catch {
+		return false;
+	}
+}
+
 const files = [];
 
 for (const basename of fs.readdirSync('src')) {
 	if (fs.statSync(`src/${basename}`).isDirectory()) continue;
 
+	const filepath = `src/${basename}`;
+	const text = is_text_file(filepath);
+
 	files.push({
 		type: 'file',
 		name: basename,
 		basename,
-		contents: fs.readFileSync(`src/${basename}`, 'utf-8'),
-		text: true // TODO might not be
+		contents: fs.readFileSync(filepath, text ? 'utf-8' : 'base64'),
+		text
 	});
 }