fix: support legacy research snapshots on macOS

docs/research/portfolio-capacity-bracket.md

@@ -120,13 +120,32 @@ atomically and resume verifies a fingerprint over the implementation commit,
 this specification hash, snapshot SHA-256, cache key, arm definitions, costs,
 and cohort manifest. An authoritative run refuses a dirty worktree.
 
+The loader reads only ticker ID/symbol and the OHLCV columns used by replay, so
+snapshots created before SEC metadata added `tickers.cik`, `tickers.sic`, and
+`tickers.sic_description` remain valid. Do not migrate or alter the research
+snapshot: its original SHA-256 is part of the run fingerprint.
+
+macOS environment setup from the repository root (zsh):
+
+    python3 -m venv .venv
+    ./.venv/bin/python -m pip install -e '.[dev]'
+
 Preflight:
 
-    python scripts/run_portfolio_construction_matrix.py backtest_snapshots/research.sqlite --run-id prod505-capacity-bracket-daily-v1 --validate-only
+    ./.venv/bin/python scripts/run_portfolio_construction_matrix.py \
+      backtest_snapshots/research.sqlite \
+      --run-id prod505-capacity-bracket-daily-v1 \
+      --workers auto \
+      --resume \
+      --validate-only
 
 Authoritative run:
 
-    python scripts/run_portfolio_construction_matrix.py backtest_snapshots/research.sqlite --run-id prod505-capacity-bracket-daily-v1 --workers auto --resume
+    ./.venv/bin/python scripts/run_portfolio_construction_matrix.py \
+      backtest_snapshots/research.sqlite \
+      --run-id prod505-capacity-bracket-daily-v1 \
+      --workers auto \
+      --resume
 
 Commit only the compact final JSON and Markdown reports. Raw curves, trades,
 candidate caches, and checkpoints remain ignored.