perf(core): cache measureFunc results in TextBufferRenderable

[remorses]

Summary

Adds a measure cache to TextBufferRenderable to avoid redundant measureForDimensions calls during Yoga layout passes.

Why Yoga calls measureFunc multiple times:

During flexbox layout, Yoga probes nodes with different width constraints to determine optimal sizing:

1. First with Undefined mode to get intrinsic size
2. Then with AtMost to constrain to available space
3. Sometimes again with Exactly after resolving flex grow/shrink

This means measureForDimensions (which does text wrapping calculations) was being called 2-3x per layout pass per text node.

Solution:

• Add _version counter to TextBuffer that increments on content changes
• Cache measure results in TextBufferRenderable keyed by width
• Invalidate cache when textBuffer.version changes or wrapMode changes

Benchmark results (144 text renderables in 8x6 grid):

Cached renders (no content change): 1.04ms avg
Uncached renders (content changes): 5.44ms avg

Cache speedup: 5.3x faster when content unchanged

References #433 (comment)

[Copilot]

Pull request overview

This PR implements a measure cache in TextBufferRenderable to avoid redundant text measurement calculations during Yoga layout passes. During flexbox layout, Yoga often calls the measure function 2-3 times with different width constraints to determine optimal sizing, causing wasteful recomputation of text wrapping. The optimization adds version tracking to detect content changes and caches measurement results by width, providing a 5.3x speedup for unchanged content.

Key changes:

• Added version counter to TextBuffer that increments on all content mutations
• Implemented measure cache in TextBufferRenderable keyed by floored width with version-based invalidation
• Added benchmark to validate the performance improvement

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 1 comment.

File	Description
packages/core/src/text-buffer.ts	Adds _version counter incremented by all content-mutating methods (setText, append, loadFile, setStyledText, clear, reset) and exposes it via a getter
packages/core/src/renderables/TextBufferRenderable.ts	Implements measure cache with Map keyed by floored width, invalidated on version changes and wrap mode changes
packages/core/src/benchmark/measure-cache-benchmark.ts	Adds benchmark comparing cached vs uncached render performance with 144 text renderables in a grid layout
.gitignore	Adds *.cpuprofile to ignore CPU profiling output files

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[kommander]

The EditorView uses the measureForDimensions as well. I'd put that in the native TextBufferView to have the cache work for both.

Also, the measure function caused a lot of issues in the past, I am very vary. I think there are some invalidations missing, like when wrapMode or viewport changes for example.

[remorses]

Ok I moved the cache inside TextBufferView. Benchmark still shows 5x faster

Added also more invalidations