fix: free lazily allocated storage on failed init and only permit lazy allocation for old-style constructors

If an old-style placement-new `__init__`/`__setstate__` failed after
`self` was loaded, the lazily allocated storage stayed behind with a
null-holder instance, so the uninitialized-value guard never fired again
and later use read uninitialized memory. `instance_construction_scope`
now tracks the constructor's `value_and_holder` and frees storage that
was lazily allocated during a construction that did not complete.

Also arm the scope only when the overload chain contains an old-style
constructor. New-style constructors receive `self` directly and never
need lazy allocation, so reentrant loads of the half-built instance now
raise `ValueError` instead of handing out uninitialized storage.

Assisted-by: ClaudeCode:claude-fable-5
Claude-Session: https://claude.ai/code/session_01TQXCSykMn5EL7sc6VgTUTC