feat: add placeholder height for topic content area

[graycreate]

Summary

Add minimum height placeholder for the topic content area while content is rendering to prevent layout jumps.

Changes

• Add contentReady state to track when RichContentView finishes rendering
• Use onRenderCompleted callback to detect render completion
• Apply 60% screen height as minimum height while loading
• Animate transition to actual content height when ready

Test plan

• Open a topic detail page
• Observe that content area maintains stable height during loading
• Verify smooth transition when content renders
• Confirm no layout jumps occur

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR adds a placeholder height mechanism to the topic content area to prevent layout jumps during content rendering. The implementation introduces state tracking to detect when RichContentView completes rendering and applies a minimum height constraint that transitions away once content is ready.

Key Changes

• Introduces contentReady state to track RichContentView rendering completion
• Utilizes the onRenderCompleted callback to detect when content finishes rendering
• Applies a 60% screen height minimum constraint while loading, transitioning to actual content height

[Copilot]

Using UIScreen.main.bounds directly in SwiftUI is not the recommended approach and can cause issues with multitasking on iPad, scene-based apps, and dynamic sizing. The preferred approach is to use GeometryReader to get the size of the containing view. Replace UIScreen.main.bounds.height * 0.6 with a GeometryReader-based solution to get the proper container height.

[Copilot]

The animation wrapper around the state change in onRenderCompleted will not animate the frame transition. The withAnimation block animates the state change itself, but the frame modifier on line 50 doesn't implicitly animate. To achieve smooth height transition, either remove the withAnimation wrapper (since the frame change will be instantaneous anyway) or move the animation modifier to the frame itself using .animation(.easeInOut(duration: 0.2), value: contentReady) after the frame modifier.

Suggested change

	withAnimation(.easeInOut(duration: 0.2)) {
	contentReady = true
	}
	}
	.padding(.horizontal, 12)
	.padding(.vertical, 8)
	.frame(minHeight: contentReady ? 0 : UIScreen.main.bounds.height)
	contentReady = true
	}
	.padding(.horizontal, 12)
	.padding(.vertical, 8)
	.frame(minHeight: contentReady ? 0 : UIScreen.main.bounds.height)
	.animation(.easeInOut(duration: 0.2), value: contentReady)

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