1\section{Reproducibility, data access and prospective design}\label{sec:repro}23\paragraph{Code and outputs.} The pipeline (Python 3.12; pinned dependencies) runs from the raw snapshot to the compiled paper with \texttt{make}: ingestion to Parquet with checksum verification, unit normalisation, retailer hierarchy, daily and weekly panel reconstruction (DuckDB), tiered matching with UPC calibration and LLM second annotation, Models A--F, QGPAI, robustness, LaTeX tables and vector figures. Every stochastic step uses seed 20261101. Each stage writes a manifest with SHA-256 hashes of its outputs and a line in a structured run ledger; model scripts write JSON summaries from which all numbers in the text and tables are generated. Fifteen tests (unit parsing, panel invariants, matching rules, output consistency) pass. The preregistration and basket were hashed before estimation; the decision log records three amendments. The LLM second annotation (claude-opus-5-5, four runs, 1.58~USD, model and tokens logged) is auxiliary: its labels are stored, so the pipeline runs without API access.45\paragraph{Data access.} The raw snapshot is a read-only export of a database owned by the author and is not redistributed in the repository; it can be made available to referees under a data-use agreement, together with the SHA-256 of the file used here. Food-Ka's \texttt{robots.txt} disallows automated access to its API; the public API was queried once to cross-check headline counts and is not a data source. Statistics Canada series were obtained from the public Web Data Service (tables 18-10-0004-01 and 18-10-0245-01; raw JSON kept with download timestamps).67\paragraph{Prospective collection design (not implemented here; no production change was made).} (i) Store selection: pin a fixed panel of about twenty stores across Quebec regions in the Loblaw, Metro and Walmart connectors and pull Flipp circulars for at least six postal codes (Montréal, Québec, Gatineau, Sherbrooke, Saguenay, Trois-Rivières), one pass per store per day. (ii) Regular-price logging: add regular price and on-sale flag to the price log. (iii) Package-label logging: keep a history of size labels to detect downsizing. (iv) Duration: 26 weeks for promotion recurrence and reference-price tests, 52 weeks for seasonality and validation against official indices. The authorisation is the owner's; the changes are reversible and polite.89\paragraph{Use of AI assistance.} The pipeline, the analyses and the drafting of this manuscript were produced by the author with an AI research assistant (Claude Code) operating under the written mandate reproduced in the repository; all design decisions, amendments and the validation review are documented and the author is responsible for the content. No coauthor or institutional approval is implied.10