Add multilingual language and systems learning tracks

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+<!doctype html><html lang="en"><meta charset="utf-8"><title>Collections and repeated work</title><h1>Collections and repeated work</h1><p>15-minute session: read for 3 minutes, trace for 3, experiment for 7, and complete the check for 2. Spend longer whenever you need.</p><p>A collection stores related values. The loop visits 1, 2, and 3, updating the total from 0 to 1, then 3, then 6. Record this trace rather than guessing. Identify the first and last valid positions in this language: Pascal can declare a 1-based array, while many other examples use zero-based containers. Add another value and update the bounds correctly. Explain what an empty collection should produce.</p><p><code>let</code> introduces an immutable binding and <code>var</code> a mutable one. Converting text with <code>Int(raw)</code> may produce <code>nil</code>. <code>if let</code> unwraps a present value without force-unwrapping missing data.</p><pre><code class="language-swift">let minutes = [1, 2, 3]
+var total = 0
+for value in minutes { total += value }
+print(total)
+</code></pre><p><strong>Expected result:</strong> <code>6</code></p><h3>Practice and evidence</h3><p>Keep three notes: your prediction, the actual result, and why they match or differ. The completion check grades understanding; the practice task builds skill.</p><p><a href="https://docs.swift.org/swift-book/documentation/the-swift-programming-language/">Language reference</a></p></html>