perf(webf): land flex layout optimization and profiling stack

[andycall]

Scope
This PR contains the full local stack currently ahead of origin/main.

Included commits

• feat: add agent skills
• profiler: add profiler test specs.
• perf(webf): reduce relayouts in flex fast path
• fix(webf): restore stable flex layout behavior
• perf(webf): reduce redundant flex fast-path relayouts
• perf(webf): narrow mixed flex measurement reuse
• perf(webf): skip futile early flex run-metrics passes
• perf(webf): reduce layout constraint overhead
• perf(webf): optimize layout hotspots
• perf(webf): narrow flex cache reuse under wrapped layouts
• perf(webf): optimize flex hotspot profiling
• fix(webf): avoid debug-only layout reuse checks
• fix(webf): correct widget layout reuse in flex

Summary
Tooling and profiling

• add the WebF agent skills set under .agents/skills
• add Android hotspot profiling test support and runner updates in integration_tests
• add focused hotspot profiling coverage for layout-heavy cases

Layout and rendering changes

• optimize hot flex and layout paths across flex.dart, box_model.dart, flow.dart, inline_formatting_context.dart, render_style.dart, length.dart, and related rendering code
• reduce redundant relayout work in flex measurement and adjustment phases
• preserve percentage-sensitive flex sizing and row percentage width resolution
• tighten cache reuse rules under wrapped layouts and auto-sized widget-backed flex items
• replace unsafe debug-only layout reuse checks with runtime-safe behavior
• narrow text invalidation so IFC rebuilds do not violate Flutter relayout boundaries

Validation

• Integration slice run:
  cd /Users/andycall/workspace/webf3/integration_tests && npm run integration -- specs/dom/elements/input.ts specs/dom/react_vite_app.tsx specs/css/css-flexbox/flex-grow.ts specs/css/css-text/line-join.ts
• Result: 98 specs, 0 failures, 29 pending specs
• Targeted hotspot profiling support was exercised through the Android OTC hotspot flow during development

Notes

• this PR is a stacked branch, not a single-fix branch
• unrelated local files were intentionally left out of the commits

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated (UTC)
use-case	Ready	Preview, Comment	Mar 29, 2026 6:07pm
vue_usecase	Ready	Preview, Comment	Mar 29, 2026 6:07pm