fix: prevent infinite reactive loop when computed reads @locals inside for (#140)

[rohal12]

Summary

• Fix {computed} referencing @ loop variable inside {for} causes infinite reactive loop #140: {computed _x = @item.status} inside {for @item of array} no longer causes an infinite reactive loop
• For.tsx: Decompose ForIteration props and memoize ownKeys/localState with useMemo to stabilize object references across unrelated re-renders
• Computed.tsx: Add per-instance prevRef self-comparison guard so each {computed} only writes to the store when its own output changes, preventing oscillation from conflicting writes
• Also includes design specs and plans for issues Temporary variable set by {set} not visible to next {set} in same passage #136, Feature: transient variables — reactive but excluded from history snapshots #137, and published types sync

Test Plan

• Verify {computed _derived = @item.status} inside {for} renders without hanging (regression test)
• Verify single-iteration computed + @Local produces correct output
• All 1065 existing tests pass
• npx tsc --noEmit passes clean

🤖 Generated with Claude Code

[github-actions]

Release preview: merging this PR will publish v0.43.1 (patch bump from v0.43.0)

[github-actions]

Coverage Report

Status	Category	Percentage	Covered / Total
🔵	Lines	77.35%	2825 / 3652
🔵	Statements	76.35%	3087 / 4043
🔵	Functions	69%	512 / 742
🔵	Branches	73.26%	1537 / 2098

File Coverage

File	Stmts	Branches	Functions	Lines	Uncovered Lines
Changed Files
src/components/macros/Computed.tsx	75.92%	75%	100%	78.72%	13, 14, 17-18, 20, 26-28, 35-37, 48-51, 72-76, 98-102
src/components/macros/For.tsx	91.48%	82.35%	100%	90.47%	28, 39, 42-44, 118-122
src/components/macros/WidgetInvocation.tsx	96.18%	95.28%	72.72%	97.32%	45, 201, 203, 253

Generated in workflow #215 for commit aa36a82 by the Vitest Coverage Report Action