Append lesson to documentation

Append timestamped lesson entry to docs log

Recording discoveries and learnings during active development without breaking flow

• · lesson text (ARGUMENTS)

• · appended docs/lessons.md
• · git commit with lesson timestamp

• · git

• · docs/lessons.md exists or will be created
• · cwd is project root

• · file permission denied
• · invalid git config
• · argument exceeds 72 chars after date prefix

• · clear YYYY-MM-DD timestamp format
• · enforces 72 char commit limit
• · auto-creates file header