fix: cond/if calculation in query filters causes DBConnection.EncodeError

[diogomrts]

Summary

Using a cond or if expression calculation in a query filter causes a DBConnection.EncodeError because the THEN/ELSE clause literals in the generated SQL CASE WHEN are not type-cast in the WHERE context, while they are properly cast in SELECT.

Reproduction

The PR adds a failing test that demonstrates the issue. A score_category calculation using cond is added to the Post test resource:

calculate(:score_category, :integer,
  expr(
    cond do
      score > 100 -> 3
      score > 50 -> 2
      score > 0 -> 1
      true -> 0
    end
  )
)

Loading the calculation works fine — the SQL correctly casts THEN values:

SELECT ... (CASE WHEN (score > 100) THEN 3::bigint ... END)::bigint ...

Filtering on the same calculation fails:

WHERE (CASE WHEN (score > 100) THEN 3 ... END)::bigint = 2
-- DBConnection.EncodeError: Postgrex expected a binary, got 3

The missing ::bigint casts on the THEN literals cause Postgrex to fail parameter encoding.

Root cause

The bug is in ash_sql (deps/ash_sql/lib/expr.ex).

When Ash converts cond to nested If nodes, the %If{} struct has embedded?: true. The If handler in default_dynamic_expr/6 calls do_dynamic_expr for each THEN/ELSE value, passing the resolved type (e.g. :integer). However, because embedded? is true, the call dispatches to the default_dynamic_expr(query, other, bindings, true, acc, type) clause (line ~2990), which calls handle_literal but does not apply type casting — unlike the embedded? = false clause (line ~3037) which does call parameterized_type + type_expr.

This means the THEN value 3 is passed as a raw integer into the Fragment's :casted_expr parameter with type :any. Postgrex cannot infer the correct encoding from the CASE context and defaults to text, producing the binary-vs-integer mismatch.

Impact

Any cond/if expression calculation (returning integers, floats, etc.) that is used in an Ash.Query.filter will fail. This also affects Ash policy FilterCheck modules that reference such calculations, breaking authorization on bulk operations.