feat: add extended language validators and fix tokenizer crash bugs

Expand nimcheck with validators and tokenizers for C, C++, C#, Go, Rust,
Ruby, CSS, SQL, Markdown, Dockerfile, Makefile, Kotlin, Lua, Swift,
TypeScript, and XML. Register all flavors in the validator factory and
improve auto-detection scoring for the new languages.

Fix infinite tokenizer loops that caused OOM kills: closeBracket now
advances position, finishTokenizeStep guards stalled tokenization, and
Jinja/JS tokenizers no longer double-advance on brackets.

Fix block-balance false positives in Lua (for/do) and Ruby (postfix
unless), SQL trailing-comma detection across whitespace, and Makefile
tab literals in test fixtures.

tests/fixtures/lua/edge_cases.lua

@@ -0,0 +1,64 @@
+-- Unicode comment: 你好世界 🌍🚀
+
+-- Unicode string literals
+local unicode = "こんにちは世界"
+print(unicode)
+
+-- Null byte in string
+local null_str = "hello\0world"
+print("Null-str length: " .. #null_str)
+
+-- Deeply nested tables
+local deep = {
+    a = {
+        b = {
+            c = {
+                d = {
+                    e = "deep"
+                }
+            }
+        }
+    }
+}
+print(deep.a.b.c.d.e)
+
+-- Very long string
+local long_str = string.rep("x", 10000)
+print("Long string length: " .. #long_str)
+
+-- Metatable chains
+local a = {}
+local b = {}
+local c = {}
+setmetatable(a, {__index = b})
+setmetatable(b, {__index = c})
+c.value = 42
+print("Metatable chain: " .. a.value)
+
+-- Deep function nesting
+local function level1()
+    return function()
+        return function()
+            return function()
+                return function()
+                    return 42
+                end
+            end
+        end
+    end
+end
+print("Deep functions: " .. level1()()()()())
+
+-- Coroutine with deep stack
+local co = coroutine.create(function()
+    local function recurse(n)
+        if n == 0 then
+            coroutine.yield("done")
+        else
+            return recurse(n - 1)
+        end
+    end
+    recurse(100)
+end)
+local _, msg = coroutine.resume(co)
+print("Coroutine: " .. msg)

tests/fixtures/lua/invalid.lua

@@ -0,0 +1,31 @@
+local function broken()
+    local x = 5
+    print(x)
+end
+
+local s = "unclosed string
+print(s)
+
+local function bad_if(x)
+    if x > 0
+        print("positive")
+    end
+end
+
+local function missing_end(x)
+    if x > 0 then
+        print("positive")
+end
+
+local t = {1, 2, 3
+print(t[1])
+
+local function nested()
+    local function inner()
+        local function deeper()
+            return 42
+        end
+    end
+end
+
+print("done"

tests/fixtures/lua/valid.lua

@@ -0,0 +1,57 @@
+local function add(a, b)
+    return a + b
+end
+
+local function greet(name)
+    print("Hello, " .. name .. "!")
+end
+
+local Person = {}
+Person.__index = Person
+
+function Person:new(id, name, email)
+    local obj = {
+        id = id,
+        name = name,
+        email = email
+    }
+    setmetatable(obj, self)
+    return obj
+end
+
+function Person:__tostring()
+    return self.name .. " <" .. self.email .. ">"
+end
+
+local Repository = {}
+Repository.__index = Repository
+
+function Repository:new()
+    return setmetatable({items = {}}, self)
+end
+
+function Repository:add(key, item)
+    self.items[key] = item
+end
+
+function Repository:find(key)
+    return self.items[key]
+end
+
+function Repository:getAll()
+    local result = {}
+    for _, v in pairs(self.items) do
+        table.insert(result, v)
+    end
+    return result
+end
+
+local repo = Repository:new()
+repo:add(1, Person:new(1, "Alice", "alice@example.com"))
+repo:add(2, Person:new(2, "Bob", "bob@example.com"))
+
+for _, p in ipairs(repo:getAll()) do
+    print(p)
+end
+
+print("3 + 4 = " .. add(3, 4))