fix: local function declarations

[davydog187]

Pulled from #142
Closes #144

FuncDecl Local Assignment ⭐

Fixed function f() syntax to properly update local variables:

• function f() now correctly updates local f when one exists in scope
• Scope resolution marks assignment target in var_map at declaration time
• Prevents future locals from incorrectly affecting earlier code during codegen
• Fixes common Lua pattern where local f = function()... is followed by function f()

Example fixed pattern:

local f = function(x) return "first" end
-- Later redefine f
function f(x) return "second" end
-- f now correctly refers to "second"

FuncDecl Fix:

• Scope resolution checks if local exists at FuncDecl position
• Stores target as {:func_decl_target, decl} in var_map
• Codegen uses this marker instead of checking ctx.scope.locals (which contains all function-scope locals)