fix: show falsy sample values instead of NULL in introspect_schema

[Osamaali313]

Problem

The sample-data renderer in introspect_schema formatted each cell with:

vals = [str(v)[:30] if v else "NULL" for v in row]

if v is truthiness, so every falsy column value — 0, 0.0, False, empty string, Decimal('0') — was displayed as NULL. The agent reading the schema sample then sees missing data where real values exist.

Reproduction

Running the real tool against a SQLite table with a row of (0, '', 0, 0.0):

Before

| qty | name | flag | price |
| --- | --- | --- | --- |
| NULL | NULL | NULL | NULL |
| 5 | hello | 1 | 9.5 |

After

| qty | name | flag | price |
| --- | --- | --- | --- |
| 0 |  | 0 | 0.0 |
| 5 | hello | 1 | 9.5 |

Fix

Treat only None as NULL; render every other value (including falsy ones) with str(v)[:30]:

vals = ["NULL" if v is None else str(v)[:30] for v in row]

[Copilot]

Copilot was unable to review this pull request because the user who requested the review has reached their quota limit.