fix: Fix CaseClauseError when filtering/sorting on doubly-nested embedded resource fields (#217)

`split_at_paths` accumulates path segments as it walks a `get_path` expression.
The `:bracket` arm only matched `{:bracket, path, nil, nil}` — the initial empty
state. After the first embedded hop the accumulator carries real type and
constraint info, so no clause matched and a `CaseClauseError` was raised.

Widening the pattern to `{:bracket, path, _, _}` allows consecutive JSONB
bracket accesses to keep accumulating into the same segment, which `do_get_path`
already handles correctly via `jsonb_extract_path_text(col, 'key1', 'key2', ...)`.

Author: sevenseacat

lib/expr.ex

@@ -3064,7 +3064,7 @@ defmodule AshSql.Expr do
 
       :bracket ->
         case first_acc do
-          {:bracket, path, nil, nil} ->
+          {:bracket, path, _, _} ->
             split_at_paths(type, constraints, rest, [
               {bracket_or_dot, [next | path], type, constraints}
               | rest_acc