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>

cli.py

@@ -15,6 +15,7 @@ from pipeline.data.cli import data
 from pipeline.alpha.cli import alpha
 from pipeline.combo.cli import combo
 from tools.pqcat import pqcat
+from tools.alphaview import alphaview
 
 
 @click.group()
@@ -39,6 +40,7 @@ cli.add_command(data)
 cli.add_command(alpha)
 cli.add_command(combo)
 cli.add_command(pqcat)
+cli.add_command(alphaview)
 
 
 if __name__ == "__main__":