Implements the copy-if pattern as a Lean tactic:
- 'copy_if' tries rfl → decide → omega → norm_num → simp in order
- 'copy_if?' reports which closer worked (for profiling)
- Each closer is a 'zero delta' check — if goal is in normal form,
closes instantly; if not, tries next closer
This is the Lean-native equivalent of:
- Blog post: vpcompressd register-dest = 40x faster
- VCN: numpy copy-if = 3.3x faster
- Pre-filter: skip trivial theorems = 2.7x faster
- LSP: copy_if tactic = instant close for zero-delta goals
Usage:
import Semantics.CopyIfTactic
theorem foo : 1 = 1 := by copy_if
theorem bar : x + 0 = x := by copy_if
theorem baz : complex := by copy_if -- falls through to simp
3298 jobs, 0 errors. Tests pass for rfl, decide, omega, norm_num.
