/receipts — personal Google Antigravity impact report

Generates a markdown report of one developer's own Google Antigravity activity, built entirely from local data:

• Source data: this machine's session transcripts at ~/.gemini/config/projects/**/*.jsonl (every session, every project, already on disk — nothing to set up).
• Cost: the mining step is a local Node script — file I/O + regex, zero API calls. The only model call is one final write-up over a small (~10-20KB) JSON summary, regardless of how much history was scanned.
• Cross-reference: local git log per repo (no network) to sanity-check commit activity against CC session activity.

Step 1 — figure out the period