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.sh

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+set -euo pipefail
+root=$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")/../.." && pwd)
+exec python3 "$root/scripts/benchmarks/context.py" "$@"