Render lines with round joins

[seveibar]

Summary

• emit stroke-linejoin="round" for lines in generated SVGs
• use round line joins in canvas and PNG rendering paths
• assert that every generated line polyline carries the round join
• update the acute-polyline SVG snapshot from a pointed miter to a rounded bend

Stack

• Base/repro: Add SVG snapshot for acute line joins #230 adds a focused toMatchSvgSnapshot fixture and captures the current pointed miter
• This PR applies the renderer fix and contains the resulting SVG snapshot diff

Why

Exported SVG lines fell back to SVG's miter join default, even though the interactive renderer already used rounded joins. Canvas rendering likewise only configured rounded end caps. This makes line appearance consistent across renderers and avoids sharp spikes at polyline corners.

The stacked snapshot uses a thick, acute V-shaped polyline. Before accepting the new snapshot, the matcher produced a visual diff highlighting the old triangular miter beyond the new rounded bend.

Validation

• bun test (69 passing)
• bun run format:check
• bun run build
• git diff --check

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Project	Deployment	Actions	Updated (UTC)
graphics-debug	Ready	Preview	Aug 12, 2026 6:33pm

[tscircuitbot]

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PR Rating: ⭐⭐
Impact: Minor

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