JIT: per-frame undef-var flags and skip guards on formals (#36190)

[PurHur]

Summary

• Replace module-global phpc_scope_var_init_* assigned flags with per-activation entry allocas for user-function CVs so recursive frames do not share state (matches Zend initializedSlots per frame).
• Keep module globals for {main} script CVs — marks/guards can lower in __init__ vs @main and must share one slot without LLVM dominance violations (AOT: print undefined-array-key warnings on stderr (#31991) #36081).
• Skip ZEND_CHECK_UNDEFINED_VAR for formal parameters (always defined); add unit coverage for fibo_r IR and recursion semantics vs Zend.

Test plan

./script/phpunit.sh --filter UndefinedVariableParameterGuardTest
# OK (2 tests, 9 assertions)

./script/aot-smoke.sh
# aot-smoke: 9 passed, 0 failed

make dev-verify-fast
# dev-verify-fast: OK (143s wall)

Closes #36190

Made with Cursor