docs: add API references, mapping corrections, and verification script

- Add yfinance.org and defeatbeta-api.org reference docs
- Fix defeatbeta_mapping.org: deprecated yfinance property names
  (quarterly_financials→quarterly_income_stmt, financials→income_stmt),
  longName vs longBusinessSummary conceptual mismatch, cashflow note typo
- Add Mapping Limitations section with live verification results (AAPL):
  DuckDB 1.4.3 incompatibility, format differences, coverage gaps
- Add docs/test_mapping.py as runnable mapping verification script
- Add offline.py, persistent_cache.py, download_data.py, warmup_cache.py
  for offline/cached defeatbeta usage
- Add aapl_yfinance.py exploration script and quant.py scaffold
- Add .envrc (uv layout) and update pyproject.toml + uv.lock

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

aapl_yfinance.md

@@ -0,0 +1,119 @@
+# AAPL - All yfinance Data
+
+```python
+import yfinance as yf
+import marimo as mo
+
+ticker = yf.Ticker("AAPL")
+```
+
+## Price History
+
+```python
+history = ticker.history(period="1y", interval="1d")
+mo.ui.table(history.tail(30))
+```
+
+## Dividends
+
+```python
+mo.ui.table(ticker.dividends.tail(20))
+```
+
+## Splits
+
+```python
+mo.ui.table(ticker.splits)
+```
+
+## Income Statement
+
+```python
+mo.ui.table(ticker.get_income_stmt())
+```
+
+## Balance Sheet
+
+```python
+mo.ui.table(ticker.get_balance_sheet())
+```
+
+## Cash Flow
+
+```python
+mo.ui.table(ticker.get_cashflow())
+```
+
+## Analyst Recommendations
+
+```python
+mo.ui.table(ticker.recommendations.tail(20))
+```
+
+## Analyst Target Prices
+
+```python
+mo.ui.table([ticker.target_prices])
+```
+
+## Earnings Dates
+
+```python
+mo.ui.table(ticker.earnings_dates)
+```
+
+## Options Expirations
+
+```python
+expirations = ticker.get_options()
+f"Available: {expirations}"
+```
+
+```python
+if expirations:
+    chain = ticker.option_chain(expirations[0])
+    mo.ui.table(chain.calls)
+    mo.ui.table(chain.puts)
+```
+
+## Major Holders
+
+```python
+mo.ui.table(ticker.major_holders)
+```
+
+## Institutional Holders
+
+```python
+mo.ui.table(ticker.institutional_holders)
+```
+
+## Sustainability / ESG
+
+```python
+mo.ui.table([ticker.sustainability])
+```
+
+## Calendar / Events
+
+```python
+mo.ui.table(ticker.calendar)
+```
+
+## Company Info Summary
+
+```python
+info = ticker.info
+{
+    "name": info.get("longName"),
+    "sector": info.get("sector"),
+    "industry": info.get("industry"),
+    "marketCap": info.get("marketCap"),
+    "peRatio": info.get("trailingPE"),
+    "fwdDividend": info.get("dividendYield"),
+    "52wkHigh": info.get("fiftyTwoWeekHigh"),
+    "52wkLow": info.get("fiftyTwoWeekLow"),
+    "avgTarget": info.get("targetMeanPrice"),
+    "recommendation": info.get("recommendationKey"),
+}
+```