Overview

This PR adds a newPlotly.profile() API method that enables users to diagnose
rendering performance of their Plotly charts by collecting timing data for each
phase of the rendering pipeline.

Motivation

Users often ask "why is my chart slow?" but currently have no built-in way to
diagnose where time is being spent. This profiler provides visibility into the
rendering lifecycle, helping users understand whether bottlenecks are in data
processing (doCalcdata), DOM manipulation (drawFramework), or actual drawing
(drawData).

Future direction: This MVP focuses on timing collection. Down the line, this
could potentially be extended to:

• Provide optimization suggestions based on profile data (e.g., "consider using
  scattergl for datasets > 10k points")
• Recommend optimal data structures for different trace types
• Help users choose appropriate partial bundles based on their usage

I wanted to get community feedback on the core API before expanding scope.

What this PR does

• AddsPlotly.profile(gd, [enable]) to enable/disable profiling on a graph div
• Collects timing for rendering phases: supplyDefaults, doCalcdata, drawFramework,
  drawData, etc.
• Stores results ingd._profileData after each render
• Emitsplotly_profiled event for reactive integrations
• Zero overhead when profiling is disabled

Usage

// Enable profilingPlotly.profile(gd);// Render or update a chartPlotly.react(gd,[{y:[1,2,3]}]);// Inspect timing breakdownconsole.log(gd._profileData);// { total: 45.2, phases: { supplyDefaults: {...}, doCalcdata: {...}, ...}}// Listen for profiling eventsgd.on('plotly_profiled',data=>console.log('Render took',data.total,'ms'));// Disable profilingPlotly.profile(gd,false);##Fileschangedsrc/lib/profiler.js(NEW)-Coretimingutilitysrc/plot_api/profile.js(NEW)-PublicAPImethodsrc/lib/index.js-Exportprofilermodulesrc/plot_api/index.js-Exportprofilemethodsrc/plot_api/plot_api.js-Addtiminghookstorenderingpipelinetest/jasmine/tests/profile_test.js(NEW)-Unittests##ChecklistWorkingondevbranch,notmasterMergedwithlatestupstream/masterDidNOTmodifydist/foldernpmrunlintpassesTestspass(npmruntest-jasmine--profile)Note:Thisismyfirstcontributiontoplotly.js(workingontwoPRsforthisproject).I've done my best to follow the contribution guidelines and existingcodepatterns,butI'm very open to feedback on the API design, implementationapproach,oranythingelse.Thankyoufortakingthetimetoreview!