1\appendix2\section{Supplementary material}\label{app:supp}34\subsection{Matching rules in detail}5Cleaned name key: strip accents, lower-case, remove size tokens (\texttt{\textbackslash d+ x? \textbackslash d* (kg|g|mg|lb|oz|ml|cl|l|un|ea|pk|ch)}), punctuation, stop words (de, du, des, la, le, les, et, à, pour, the, of, and, with, un, une, sans, avec, ou, or) and the brand's own tokens; append the residual of the package label (e.g.\ ``calibre 21-25'') after removing deposit and unit-price fragments; sort tokens. Numeric tokens must be identical. Package key: total quantity in base unit rounded to 0.1 and multipack count. Tier~B: identical token sets; tier~C: rapidfuzz \texttt{token\_sort\_ratio} $\ge 0.90$; tier~D: identical full-name token sets with brand tokens present. The calibration table over scorers and thresholds, the recall analysis against UPC truth, the three validation samples (the rejected token-set version, round 1 and round 2) and the LLM prompts are in the replication package.67\subsection{Preregistered hypotheses (abridged)}8H1: median within-group max--min log gap $\ge 0.05$ and AR(1) of banner-pair gaps $\ge 0.5$, placebo by label permutation. H2: ratio of raw to reference weekly volatility $\ne 1$, bootstrap over listings; falsification on single-store shops. H3: mean change of the reference price after promotion episodes $= 0$ (null), direction left to the data; event study with pretrend test, censoring and overlap rules; placebo at random dates. H4: distributed lags 0--3 with leads as placebo; geography untestable. H5: naive mean vs.\ matched-model gap $= 0$ (null), bootstrap; StatCan coherence check. H6: $S(\infty)-S(2)=0$ (null) on a 30-item basket fixed before computation. Full text, estimands, clustering and missingness rules: \texttt{research/preregistration.md} (SHA-256 in \texttt{research/decisions.md}).910\subsection{Additional tables}11Per-feed coverage for all 54 feeds, category-level gaps with Holm-corrected sign tests, volatility ratios by banner and category, index changes by banner and category, basket item coverage, block sensitivity, the travel-cost grid, and per-origin forecast errors are provided as CSV files in \texttt{data/processed/} and as JSON summaries in \texttt{experiments/}.12