SSOT principle: Pass canonicalizer-derived ConditionalStep info to Pattern2 lowerer
without re-detecting from AST.
Changes:
- router.rs: Add skeleton: Option<&'a LoopSkeleton> to LoopPatternContext
- parity_checker.rs: Return (Result, Option<LoopSkeleton>) to reuse skeleton
- routing.rs: Pass skeleton to context when joinir_dev_enabled()
- pattern2_with_break.rs: Detect ConditionalStep in can_lower()
Next: P0-3 implements actual JoinIR generation for ConditionalStep.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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