Phase 122: Remove unused ctb(int) overload

Removed the `lu_byte ctb(int)` overload from ltvalue.h as it was unused.
All ctb() calls in the codebase use LuaT enum values, which call the
`LuaT ctb(LuaT)` overload. This simplifies the API and removes dead code.

Analysis:
- Searched codebase for all ctb() calls
- All calls use LuaT::* enum values (SHRSTR, LNGSTR, etc.)
- Calls like ctb(s->getType()) pass LuaT (from GCBase::getType())
- No integer literals or LUA_T* macros passed to ctb()

Changes:
- src/objects/ltvalue.h:318 - Removed ctb(int) overload

Testing:
- Build: ✅ Success (no compilation errors)
- Tests: ✅ All pass ("final OK !!!")
- Performance: ~4.46s avg (within normal variance)

Author: claude

src/objects/ltvalue.h

@@ -315,7 +315,6 @@ inline constexpr int BIT_ISCOLLECTABLE = (1 << 6);
 
 /* mark a tag as collectable */
 constexpr LuaT ctb(LuaT t) noexcept { return static_cast<LuaT>(static_cast<int>(t) | BIT_ISCOLLECTABLE); }
-constexpr lu_byte ctb(int t) noexcept { return static_cast<lu_byte>(t | BIT_ISCOLLECTABLE); }  /* overload for base types */
 
 
 /* Macros for internal tests */