feat(benchmarks): report context the clients actually load

Read Claude /context, /skill-doctor, and its init event, and Codex debug
prompt-input, to list categories, active plugins, and installed skills that
are missing or listed without description context.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

scripts/commands/context-report.ps1

@@ -0,0 +1,4 @@
+$ErrorActionPreference = 'Stop'
+$root = Split-Path (Split-Path $PSScriptRoot -Parent) -Parent
+& python (Join-Path $root 'scripts/benchmarks/context.py') @args
+exit $LASTEXITCODE