Record t1.8.5 task evidence

pm/tasks.org

@@ -236,6 +236,24 @@
 - commit: `ac82fa6` on branch `cx`
 - tests: `./venv/bin/python -m unittest discover -s tests`; `./venv/bin/python scrape_costco.py --help`; reviewed the sample Costco summary request in `pm/scrape-giant.org` against `costco_output/raw/summary.json` and added 3-month window chunking plus mismatch diagnostics
 - date: 2026-03-16
+* [X] t1.8.5: refactor costco scraper auth and UX with giant scraper
+
+** acceptance criteria
+- remove manual auth env vars
+- load costco cookies from firefox session
+- require only logged-in browser
+- replace start/end date flags with --months-back
+- maintain same raw output structure
+- ensure summary_lookup keys are collision-safe by using a composite key (transactionBarcode + transactionDateTime) instead of transactionBarcode alone 
+
+** notes
+- align Costco acquisition ergonomics with the Giant scraper
+- keep downstream Costco parsing and shared schemas unchanged
+
+** evidence
+- commit: `c0054dc` on branch `cx`
+- tests: `./venv/bin/python -m unittest discover -s tests`; `./venv/bin/python scrape_costco.py --help`; verified Costco summary/detail flattening now uses composite receipt keys in unit tests
+- date: 2026-03-16
 * [ ] t1.9: compute normalized comparison metrics (2-4 commits)
 
 ** acceptance criteria