Fix filter pushdown for FK-linked columns not projected by the CTE

[shangyian]

Summary

When a transform reads from a source that has a FK dimension link, but doesn't project the FK column in its own output, dimension filters on that FK were silently dropped. The primary rewrite failed (column absent from declared output), and the second pass always skipped target_select, which is the only scope where top-level source tables appear.

The fix is to include target_select in the second pass when the primary rewrite failed. The FK link registered on the source node is then found in the target_select scope map, allowing _rewrite_filter_for_scope to inject the filter directly into the CTE's WHERE clause.

Test Plan

• PR has an associated issue: #
• make check passes
• make test shows 100% unit test coverage

Deployment Plan

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