refactor(core): remove dead percent guard paths from stack layout

[RtlZeroMemory]

Summary

• remove childHasPercentInMainAxis / childHasPercentInCrossAxis from layout guards
• remove corresponding dead callsites in stack measure/layout passes
• simplify stack auto-size finalize logic by dropping never-true percent fill branches

Why

• percentage strings are intentionally rejected in current API (expr(...) is the replacement)
• percent guard helpers were hardcoded false, so these branches were dead code
• this reduces cognitive overhead without changing runtime behavior

Behavior

• % strings remain rejected (unchanged)
• flex/advanced constraint passes remain intact

Tests

• npx tsx --test packages/core/src/layout/__tests__/layout.percentage.test.ts
• npx tsx --test packages/core/src/layout/__tests__/layout.auto-sizing.test.ts
• npx tsx --test packages/core/src/layout/__tests__/layout.edgecases.test.ts
• node scripts/run-tests.mjs --filter "layout\.(percentage|auto-sizing|edgecases)"

Summary by CodeRabbit

• Refactor
  • Simplified layout constraint logic by removing percentage-based sizing calculations from the layout engine.
  • Streamlined sizing computations by removing percent-driven constraint planning.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 19301eca-65a9-4f74-b351-c84a438be897

📥 Commits

Reviewing files that changed from the base of the PR and between 089115b and 5973e9b.

📒 Files selected for processing (2)

• packages/core/src/layout/engine/guards.ts
• packages/core/src/layout/kinds/stack.ts

💤 Files with no reviewable changes (1)

• packages/core/src/layout/engine/guards.ts

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📝 Walkthrough

Walkthrough

The changes remove percentage-based sizing detection from the layout engine. Two exported functions (childHasPercentInMainAxis and childHasPercentInCrossAxis) are deleted from guards.ts, and their usage is eliminated from stack.ts, simplifying constraint planning and final size computation in stack layout logic.

Changes

Cohort / File(s)	Summary
Percentage-Based Sizing Removal packages/core/src/layout/engine/guards.ts, packages/core/src/layout/kinds/stack.ts	Removed two public functions that detected percentage-based sizing hints in main and cross axes. Eliminated percent-based constraint consideration in both measureStack and layoutStack paths, including removal of hasPercentInMainAxis, fillMain, and fillCross computations. Simplified size calculations to derive from forced values and bounds constraints only.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• refactor(core): reduce layout/render hot-path allocations #228: Modifies stack layout implementation and percent-based sizing logic, with this PR removing the percent-handling paths that the other PR adds/uses.

Poem

🐰 Away with percentages, constraints now clear!
No more percent-math cluttering here,
Stack layouts dance with simplified grace,
Flex and forced values claim their rightful place. ✨

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: removing dead percent guard paths from stack layout code, which aligns with the actual deletions in guards.ts and simplifications in stack.ts.

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✨ Finishing Touches

• 📝 Generate docstrings (stacked PR)
• 📝 Generate docstrings (commit on current branch)

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch refactor/remove-percent-guard-deadpaths

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