perf(optimizer): lower simple integer min/max calls - #96

Two-argument min()/max() calls currently cross the Zend call boundary even when their operands are exact integers. This optimization lowers eligible calls to scalar comparisons, avoiding argument boxing and runtime dispatch.

The fast path accepts native integer variables, integer literals/casts, and resolved non-nullable integer instance properties. Other forms retain the existing runtime path. Casts are evaluated once, and ordinary variable evaluation behavior is preserved.

The included O2 benchmark improves from 482.56 ms to 48.01 ms (10.05x) for 10 million iterations: nine measured pairs, PHP 8.5.10 ZTS, Linux ARM64, PHPX 6a68f38. Reproduction instructions and raw samples are included in benchmark/min-max.

Validation:

• Focused PHPUnit: 3 tests, 30 assertions passed.
• Related PHPTs: 38 passed, covering nullable values, varint overflow, cast evaluation counts, side effects, short-circuiting and namespace resolution.
• Broad PHPUnit: 1,963 tests; three existing PythonModuleTest generated-code assertion failures also reproduce with the unmodified baseline optimizer.
• Independent review and git diff --check passed.