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/makefile/edge_cases.Makefile

@@ -0,0 +1,15 @@
+.PHONY: all clean
+
+CC := gcc
+CFLAGS := -O2 -Wall
+
+all: program
+
+program: main.o util.o
+	$(CC) $(CFLAGS) -o $@ $^
+
+%.o: %.c
+	$(CC) $(CFLAGS) -c -o $@ $<
+
+clean:
+	rm -f program *.o

tests/fixtures/makefile/invalid.Makefile

@@ -0,0 +1,16 @@
+.PHONY: all clean
+
+CC := gcc
+CFLAGS := -O2 -Wall
+
+all: program
+
+program: main.o util.o
+	$(CC) $(CFLAGS) -o $@
+
+%.o: %.c
+	$(CC) $(CFLAGS) -c -o $<
+	echo "unclosed
+
+clean:
+	rm -f program *.o

tests/fixtures/makefile/valid.Makefile

@@ -0,0 +1,57 @@
+.PHONY: all build release debug clean test coverage lint install uninstall
+
+NIM := nim
+NIM_FLAGS := --hints:off --warnings:off
+SRC_DIR := src
+BIN_DIR := bin
+TEST_DIR := tests
+BUILD_DIR := build
+
+SOURCES := $(shell find $(SRC_DIR) -name '*.nim')
+TESTS   := $(shell find $(TEST_DIR) -name '*.nim')
+OBJECTS := $(patsubst $(SRC_DIR)/%.nim,$(BUILD_DIR)/%.o,$(SOURCES))
+
+BINARY := $(BIN_DIR)/nimcheck
+
+all: build
+
+$(BIN_DIR):
+	mkdir -p $(BIN_DIR)
+
+$(BUILD_DIR):
+	mkdir -p $(BUILD_DIR)
+
+$(BUILD_DIR)/%.o: $(SRC_DIR)/%.nim | $(BUILD_DIR)
+	$(NIM) compile --compileOnly -d:release -o:$@ $<
+
+$(BINARY): $(OBJECTS) | $(BIN_DIR)
+	$(NIM) compile -d:release --out:$(BINARY) $(SRC_DIR)/nimcheck.nim
+
+build: $(BINARY)
+
+release:
+	$(NIM) compile -d:release --opt:speed --passC:-flto --passL:-flto \
+		--out:$(BINARY) $(SRC_DIR)/nimcheck.nim
+
+debug:
+	$(NIM) compile -d:debug --lineDir:on --stacktrace:on \
+		--out:$(BINARY) $(SRC_DIR)/nimcheck.nim
+
+test: build
+	$(NIM) compile --run $(TEST_DIR)/test_all.nim
+
+coverage:
+	$(NIM) compile --run -d:coverage $(TEST_DIR)/test_all.nim
+
+lint:
+	$(NIM) check $(SRC_DIR)/nimcheck.nim
+
+clean:
+	rm -rf $(BIN_DIR) $(BUILD_DIR)
+	find . -name 'nimcache' -type d -exec rm -rf {} + 2>/dev/null || true
+
+install: release
+	install -m 755 $(BINARY) /usr/local/bin/nimcheck
+
+uninstall:
+	rm -f /usr/local/bin/nimcheck