Expression index with correlated EXISTS subquery causes panic

[LeMikaelF]

Description

An expression index combined with a correlated EXISTS subquery causes the planner to fail resolving column references through the expression index.

Reproducer

CREATE TABLE t(b, c);
CREATE UNIQUE INDEX idx ON t(c, c + b);
SELECT c + b FROM t WHERE EXISTS (SELECT 1 FROM t AS t2 WHERE t.b = t2.b);
-- Turso:  PANIC
-- SQLite: (works correctly)

Panic Message

thread 'main' panicked at core/translate/expr.rs:2642:41:
index idx does not contain column number 0 of table t1

core/translate/expr.rs:2642 - The planner tries to resolve column references through the expression index but fails when a correlated subquery references columns not directly in the index.

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This issue brought to you by Mikaël and Claude Code.

[turso-github-handyman]

Fix is ready for review: compare with main