Add INP as Core Web Vital for Playwright probes and deprecate FID

[m0nkey]

Adopt INP as Core Web Vital and deprecate FID

INP (introduced May 2023) replaced FID as the responsiveness Core Web Vital (March 2024; FID removed from Chrome tools Sept 2024). This adds INP collection for Playwright probes and keeps FID as a deprecated, backward-compatible metric for now. FID should be considered for complete removal.

Changes

• lib/upright/playwright/inp_observer.js (new)
  • Init script that observes event and first-input via PerformanceObserver, tracks worst interaction by interactionId, stores value in window.upright.inp.
• app/models/concerns/upright/playwright/lifecycle.rb
  • Calls context.add_init_script(script: inp_observer_script) before new_page; script loaded with File.read(Engine.root.join(...)) like OtelTracing.
• lib/upright/playwright/collect_performance_metrics.js
  • Reads window.upright?.inp, assigns metrics.inp with Math.round (same pattern as other metrics). FID still collected; JSDoc @deprecated Use INP for responsiveness.
• README
  • OpenTelemetry: new “Browser performance (Playwright)” note that spans get browser.performance.* (ttfb, fcp, lcp, inp, fid), INP is responsiveness metric, FID deprecated.
• CHANGELOG
  • [Unreleased]: INP added, FID deprecated.

Tests

• inp observer script is injected into context
  • Stub config_for(:playwright) and connect_to_browser_server → MockBrowser/MockContext; assert init script contains window.upright, inp, PerformanceObserver.
• browser performance metrics including inp are attached to document span
  • Stub page.evaluate to return hash with inp/ttfb/fcp; assert span receives set_attribute("browser.performance.inp", …) etc.
• MockPlaywrightHelper
  • MockContext: add_init_script + init_script; MockPage: wait_for_load_state, evaluate.
• FID remains on spans as browser.performance.fid; Playwright probe tests pass.