quantmodel — Fold proxy stitching + pre-1993/pre-1980 TR into ensure

Objective

Fold proxy stitching + pre-1993/pre-1980 TR into ensure_universe wrapper.

Notes: ensure_universe + ensure_tbill; virtual __GSPC_SHILLER_TR__/__DGS10_CM_TR__; 22 datastore tests. Findings: ensure-universe-t133.md

Approach

Reuses existing report research/findings/ensure-universe-t133.md — tables/metrics preserved verbatim via source_report pointer. Body below summarizes grounded evidence from that report and adjacent artifacts.

Files / code / data changed

Associated commits (inferred from log grep t133):

e8ed67d3 research: t133 ensure_universe (proxies/chains/pre1980) (#119)
15783ddf research: mark t132 done on main; handoff t133 ensure_universe
e8ed67d3 research: t133 ensure_universe (proxies/chains/pre1980) (#119)
Source report: research/findings/ensure-universe-t133.md
Task-history entry: research/findings/task-history.json#t133

Results

Key table from source report (preserved):

Piece	Path
`ensure_universe`	`backtest/datastore.py`
`ensure_tbill_daily_returns`	same (`^IRX` via `ensure_ohlcv`)
Virtual TR tickers	`__GSPC_SHILLER_TR__`, `__DGS10_CM_TR__` (`synthetic_cm_bond_tr_ticker`)
Offline stitch / pre1980 / tbill tests	`tests/test_datastore.py` (22 total)

Conclusions and metrics are in research/findings/ensure-universe-t133.md; see detail page for preserved tables/metrics.

Conclusions

[reconstructed — uncertain] Outcome inferred from status done and task note.

Problems / follow-ups

See source report or PR discussion for follow-ups. No unsupported follow-ups fabricated.