docs(readme): add verification coverage output example

Show the coverage tracking output in README example. Details about
what's verified vs skipped are in FORMAL_VERIFICATION_GUIDE.md,
keeping the README evergreen.

Author: avrabe

README.md

@@ -168,9 +168,10 @@ cargo build --release --features verification
 ```
 🔬 Running Z3 SMT verification...
   ✅ Z3 verification passed: optimizations are semantically equivalent
+  📊 Verification coverage: 42 verified, 3 skipped (93.3%)
 ```
 
-Z3 verification proves mathematically that optimizations preserve program semantics via translation validation.
+Z3 verification proves mathematically that optimizations preserve program semantics via translation validation. The coverage report shows how many functions were fully verified vs. skipped (due to unsupported patterns like complex loops). See `docs/FORMAL_VERIFICATION_GUIDE.md` for details.
 
 ## 💡 Examples