Fix Moo support: stash keys, &{} overload, and local @_ in eval

[fglock]

Summary

This PR fixes several issues discovered while improving Moo CPAN module support:

Phase 22: Stash Keys and Overload Handling

• Fixed stash keys for nested packages - keys %Foo::Bar:: now correctly returns Baz:: (with trailing ::) instead of Baz
• Fixed &{$blessed_obj} handling - Now correctly throws "Not a subroutine reference" for blessed objects without &{} overload

Phase 23: Local @_ in String Eval

• Fixed local @_ = (...) in string eval to use register-based localization instead of global @main::_
• This was critical for Sub::Quote's inlinification pattern used by Moo for coerce/trigger/isa

Files Changed

• HashSpecialVariable.java - Fixed nested package stash key formatting
• RuntimeCode.java - Added &{} overload check in createCodeReference
• BytecodeCompiler.java - Added isReservedVariable() check for register-based local
• CompileAssignment.java - Updated to use register-based PUSH_LOCAL_VARIABLE for @_
• dev/design/moo_support.md - Updated design doc with Phase 22 and 23

Test Results

• Moo tests: 62/71 programs passing (87%), 768/829 subtests (93%)
• All remaining failures are expected due to Java limitations (weak refs, DESTROY)

Test plan

• All existing unit tests pass
• Moo test suite shows improvement (49/49 on method-generate-accessor.t)
• t/load_module_role_tiny.t now passes
• t/coerce-1.t now fully passes

Generated with Devin

[fglock]

Additional Fix: Glob Aliasing Regression

Added a fix for the mro/isa_aliases.t regression (11/13 → 13/13 now passing).

Root Cause: When *a = *b is followed by *a = \@x, both aliased globs should be updated because they share the same glob slots. Previously, only the directly assigned glob was updated, breaking ISA resolution.

Solution: Added glob alias tracking:

• GlobalVariable.globAliases map tracks which globs share slots
• getGlobAliasGroup() returns all globs aliased to the same target
• When assigning array/hash refs to a glob, all aliased globs are updated

This also fixes previously failing tests 10 and 12 in mro/isa_aliases.t (going from 11/13 to 13/13).