fix: responsive diagram layout

[anniexwang]

Proposed Changes

This PR makes the diagram screen responsive by stacking the CADiagram and ComponentSidebar horizontally for smaller screen sizes (900px). It also replaces fixed width/heights with dynamic ones.

Screenshots of your changes (if applicable)

Screen.Recording.2026-07-28.at.8.47.03.PM.mp4

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Type	Applies?
🚨 Breaking change (fix or feature that would cause existing functionality to change)
✨ New feature (non-breaking change that adds functionality)
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🎨 User interface change (change to user interface; provide screenshots)	x
♻️ Refactoring (internal change to codebase, without changing functionality)
🚦 Test update (change that only adds or modifies tests)
📦 Dependency update (change that updates a dependency)
🔧 Internal (change that only affects developers or continuous integration)

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[matt-dahlgren]

lgtm Annie great work!