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/c/edge_cases.c

@@ -0,0 +1,40 @@
+#include <stdio.h>
+#include <string.h>
+#include <wchar.h>
+#include <locale.h>
+
+/* Unicode in comments: Привет, 世界, 🌍 */
+
+int main(void) {
+    setlocale(LC_ALL, "");
+
+    /* Unicode string literals */
+    wchar_t *greeting = L"こんにちは";
+    wprintf(L"%ls\n", greeting);
+
+    /* Null byte embedded */
+    char buf[] = "Hello\x00World";
+    printf("Length: %zu\n", strlen(buf)); /* stops at null byte */
+
+    /* Deeply nested structs */
+    struct a { int x; };
+    struct b { struct a a; };
+    struct c { struct b b; };
+    struct d { struct c c; };
+    struct e { struct d d; };
+    struct f { struct e e; };
+    struct f val = {{{{{{42}}}}}};
+    printf("%d\n", val.e.d.c.b.a.x);
+
+    /* Very long function name */
+    void this_is_an_extremely_long_function_name_that_goes_on_and_on_and_on(void) {
+        printf("deep\n");
+    }
+    this_is_an_extremely_long_function_name_that_goes_on_and_on_and_on();
+
+    /* Encoding: BOM-like byte sequences */
+    unsigned char raw[] = {0xEF, 0xBB, 0xBF, 'A', 'B', 'C', 0};
+    printf("%s\n", raw);
+
+    return 0;
+}

tests/fixtures/c/invalid.c

@@ -0,0 +1,26 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#define MAX 10
+
+int main(void) {
+    int x = 5
+    printf("x is %d\n", x)
+
+    char *s = "unclosed string;
+    printf("%s\n", s);
+
+    int arr[3] = {1, 2, 3;
+    printf("%d\n", arr[1]);
+
+    if (x > 0 {
+        printf("positive\n");
+    }
+
+    char *p = malloc(10;
+    free(p);
+
+    struct { int a; int b; } s = {1, 2};
+    s.a = ;
+
+    return 0;

tests/fixtures/c/valid.c

@@ -0,0 +1,36 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define MAX_NAME 64
+#define GREETING "Hello, World!"
+
+typedef struct {
+    int id;
+    char name[MAX_NAME];
+    double score;
+} Player;
+
+int add(int a, int b) {
+    return a + b;
+}
+
+void greet(const char *name) {
+    printf("%s, %s!\n", GREETING, name);
+}
+
+int main(void) {
+    Player p = {1, "Alice", 95.5};
+    greet(p.name);
+
+    int result = add(3, 4);
+    printf("3 + 4 = %d\n", result);
+
+    FILE *fp = fopen("test.txt", "w");
+    if (fp) {
+        fprintf(fp, "id=%d,name=%s,score=%.1f\n", p.id, p.name, p.score);
+        fclose(fp);
+    }
+
+    return 0;
+}