fix(explore): handle single -F flag as array to prevent TypeError

[sentry]

This PR addresses CLI-28C, a TypeError occurring in the explore command.

Root Cause:
The flags.field argument in src/commands/explore.ts is defined as variadic: true. However, when a user supplies only a single -F flag, the CLI parser assigns a string to flags.field instead of a single-element array. The command function then blindly assigns fieldList = flags.field, making fieldList a string. Subsequent calls to .find() on fieldList (e.g., in resolveDatasetConfig or findFirstAggregate) then fail with TypeError: e.find is not a function because strings do not have a .find() method.

Fix:
To resolve this, flags.field is now explicitly coerced to an array before being assigned to fieldList. This ensures that fieldList is always an array, regardless of whether one or multiple -F flags were provided, thus preventing the TypeError.

Fixes CLI-28C

_{Comment @sentry <feedback> on this PR to have Autofix iterate on the changes.}

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Codecov Results 📊

✅ Patch coverage is 100.00%. Project has 5496 uncovered lines.
✅ Project coverage is 81.74%. Comparing base (base) to head (head).

Coverage diff

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+ Coverage    81.74%    81.74%        —%
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  Files          428       428         —
  Lines        30106     30106         —
  Branches     19593     19585        -8
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+ Hits         24611     24610        -1
- Misses        5495      5496        +1
- Partials      2054      2056        +2

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[jared-outpost]

Good catch from Warden, Seer, and Bugbot — all three flagged the same real gap: the original fix only coerced the local fieldList, so a single -F left flags.field as a bare string in hintFlags = { ...flags }. That string then hit .filter/.join in appendFieldHints (via appendFlagHints) and threw the same TypeError after a successful query.

Fixed by normalizing once at the source (normalizeFields) so fieldList, hintFlags, and contextKey all see an array. Added a regression test that reproduces the crash by passing field as a string (verified it fails without the fix, in the hint path at explore.ts:340).

Also rebased onto main (was 30 commits behind) and confirmed the bug still reproduced there before fixing.