Add multilingual language and systems learning tracks

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+<!doctype html><html lang="en"><meta charset="utf-8"><title>Lock scope and ownership</title><h1>Lock scope and ownership</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 lock protects an invariant only when every relevant access follows the same rule. Protect the whole read-modify-write operation, not just the final assignment. Define a consistent lock order when multiple locks are needed. A global lock may be correct but limit throughput; measure before splitting it.</p><p><strong>Practice and evidence:</strong> Predict the example or draw its state transitions. Change one assumption, test the boundary, and record the actual result. Explain what this small model does not establish about a production system.</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></html>