[perf] Replace static inline styles in RelatedSuggestions with CSS classes

[github-actions]

Summary

Replaces 2 static style=\{\{}} objects on Text components in RelatedSuggestions.tsx with CSS module classes.

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Tier

Tier 2 — Render & API Performance (inline style=\{\{}} elimination)

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Baseline

RelatedSuggestions.tsx rendered two Text components with static inline style objects:

// Line 110 — suggestion title
(Text style=\{\{ fontWeight: 600 }}){suggestion.title}(/Text)

// Lines 115–119 — suggestion reason
(Text style=\{\{ fontStyle: 'italic', color: 'var(--fgColor-muted)' }})
  {suggestion.reason}
(/Text)

Both objects are static (their values never change based on props or state). Static inline style objects create a new object reference on every render, forcing React to diff the style prop even though nothing changed, and the browser to re-evaluate computed styles unnecessarily.

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Fix

Added two CSS classes to the .relatedSuggestion* section in ChallengeSandbox.module.css:

.suggestionTitle {
  font-weight: var(--base-text-weight-semibold);
}

.suggestionReason {
  font-style: italic;
  color: var(--fgColor-muted);
}

Updated RelatedSuggestions.tsx to use className instead:

(Text className={styles.suggestionTitle}){suggestion.title}(/Text)
(Text className={styles.suggestionReason}){suggestion.reason}(/Text)
```

No visual difference — the rendered output is identical.

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## Result

- 2 static `style=\{\{}}` objects removed from the render hot path
- Styles are now browser-cached as part of the CSS module (computed once, referenced by class name)
- Consistent with the project-wide pattern of using CSS modules over inline styles

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## Verification

```
Test Files  3 failed | 60 passed (63)   ← same 3 pre-existing failures (github/client.test.ts)
      Tests  10 failed | 1025 passed (1035)   ← no new failures

All 1025 passing tests continue to pass. The 10 pre-existing failures are unrelated (GitHub auth mock issues in client.test.ts).

Generated by Daily Performance Improver

[github-actions]

Pull request created: #107