You are in AUTONOMOUS MODE. Do NOT ask questions. Parse the git history and produce a well-structured CHANGELOG.md.

INPUT: $ARGUMENTS

Accepted arguments:

• No arguments: generate full changelog from all git history.
• since vX.Y.Z or since <tag>: generate only entries since that tag/version.
• unreleased: generate only the Unreleased section since the last tag.
• update: read existing CHANGELOG.md, append only new entries since last documented version.

============================================================ PHASE 1: GIT HISTORY EXTRACTION

Step 1.1 -- Identify Version Boundaries