Add explanatory comments

Code should include explanatory comments when the purpose, behavior, or context is not immediately clear from reading the code itself. This is especially important for:

• Non-obvious implementation decisions: When code deviates from expected patterns or removes common safeguards, explain why.
• Complex data structures: Interface fields, especially those with specific usage patterns or constraints, should be documented.
• Important behavioral details: When functionality has side effects or specific requirements that affect how it should be used.
• Context-dependent logic: Code that requires understanding of broader system behavior or migration patterns.

Example:

// Before - unclear why early return was removed
if (ngDevMode) {
  // ... complex logic
}

// After - explains the reasoning
if (ngDevMode) {
  // Note: Early return removed to ensure proper cleanup in all code paths
  // ... complex logic
}

// Before - unclear field purpose
export interface ProjectedSignalNode {
  propertyNode: ReactiveNode | undefined;
  lastProperty: PropertyKey | undefined;
}

// After - explains field usage
export interface ProjectedSignalNode {
  // Only used when the projectedSignal key argument is reactive
  propertyNode: ReactiveNode | undefined;
  // Tracks the last accessed property for change detection
  lastProperty: PropertyKey | undefined;
}

Comments should focus on the “why” rather than the “what” - explaining the reasoning, constraints, or important context that future developers need to understand when modifying or using the code.