Add context window analysis script for Reddit post

Standalone Python script that parses Claude Code JSONL session files
to visualize context growth, cache hit/miss patterns, and token usage
before vs after the 1M context window rollout. Auto-detects Claude
data directory on Windows/Mac/Linux. Requires matplotlib + numpy.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: RyanSeanPhillips