From #58 (Template Inheritance - Phase 5) code review. Deep correctness improvement: carry source identity through splice_skeleton so a base-default block's validation span points at the BASE source rather than the child, restoring precise line:col for cross-source spans. The CRITICAL panic is already closed by the boundary-safe compute_line_column degrade (commit b95a0ed), so this is non-urgent defense-in-depth hardening rather than a blocking security fix. Aligns with security principle of precise error attribution across template inheritance.
From #58 (Template Inheritance - Phase 5) code review. Deep correctness improvement: carry source identity through splice_skeleton so a base-default block's validation span points at the BASE source rather than the child, restoring precise line:col for cross-source spans. The CRITICAL panic is already closed by the boundary-safe compute_line_column degrade (commit b95a0ed), so this is non-urgent defense-in-depth hardening rather than a blocking security fix. Aligns with security principle of precise error attribution across template inheritance.