feat: add alphaview tool to show alpha weights alongside bar data

Joins the bar dataset with one or more alpha parquet files on (symbol, date)
for a given symbol and date range. Standalone tools/alphaview.py wired as
`cli.py alphaview`, plus README docs.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

README.md

@@ -179,6 +179,31 @@ ln -sf "$(pwd)/tools/pqcat.py" ~/.local/bin/pqcat   # ~/.local/bin must be on PA
 pqcat alphas/reversal_5d.pq --info
 ```
 
+### `alphaview` — alpha weight(s) alongside bar data for one symbol
+
+Join the bar dataset and one or more alpha parquet files on `(symbol, date)` and
+print them side by side, so you can eyeball how a weight moves against price /
+volume over a time range.
+
+| Option | Default | Description |
+| --- | --- | --- |
+| `--data-path` | (required) | Bar dataset dir or parquet file |
+| `--alpha-path` | (required) | Comma-separated alpha parquet path(s) — each `alpha_name` becomes a column |
+| `--symbol` | (required) | Symbol id, e.g. `sh600000` |
+| `--start-date` | — | `YYYY-MM-DD` (inclusive) |
+| `--end-date` | — | `YYYY-MM-DD` (inclusive) |
+| `-c, --columns` | `close,volume` | Comma-separated bar columns to show |
+
+```bash
+python3 cli.py alphaview \
+    --data-path data/daily_bars/csi500 \
+    --alpha-path alphas/reversal_5d.pq,alphas/momentum_5d.pq \
+    --symbol sh600000 --start-date 2024-01-01 --end-date 2024-03-31 \
+    -c close,volume,vwap
+```
+
+Also standalone like `pqcat` — `ln -sf "$(pwd)/tools/alphaview.py" ~/.local/bin/alphaview`.
+
 ## Alphas: the factory / plugin interface
 
 An **alpha** is a class that maps a wide close matrix (date index × `symbol_id`
@@ -272,6 +297,7 @@ directory yields an extra `month` (`YYYY-MM`) partition column on top of
 - `pipeline/common/schema.py` — parquet column contracts
 - `data/downloader.py`, `data/universe.py` — baostock/akshare download + constituents
 - `tools/pqcat.py` — standalone parquet inspector (`pqcat`), also wired as `cli.py pqcat`
+- `tools/alphaview.py` — standalone alpha-vs-bar viewer (`alphaview`), also wired as `cli.py alphaview`
 - `examples/alphas/` — example external alpha(s)
 
 ## Roadmap (not yet implemented)