Initial commit: Pugz - Pug-like HTML template engine in Zig

Features:
- Lexer with indentation tracking and raw text block support
- Parser producing AST from token stream
- Runtime with variable interpolation, conditionals, loops
- Mixin support (params, defaults, rest args, block content, attributes)
- Template inheritance (extends/block/append/prepend)
- Plain text (piped, dot blocks, literal HTML)
- Tag interpolation (#[tag text])
- Block expansion with colon
- Self-closing tags (void elements + explicit /)
- Case/when statements
- Comments (rendered and silent)

All 113 tests passing.

src/tests/helper.zig

@@ -0,0 +1,24 @@
+//! Test helper for Pugz engine
+//! Provides common utilities for template testing
+
+const std = @import("std");
+const pugz = @import("pugz");
+
+/// Expects the template to produce the expected output when rendered with the given data.
+/// Uses arena allocator for automatic cleanup.
+pub fn expectOutput(template: []const u8, data: anytype, expected: []const u8) !void {
+    var arena = std.heap.ArenaAllocator.init(std.testing.allocator);
+    defer arena.deinit();
+    const allocator = arena.allocator();
+
+    var lexer = pugz.Lexer.init(allocator, template);
+    const tokens = try lexer.tokenize();
+
+    var parser = pugz.Parser.init(allocator, tokens);
+    const doc = try parser.parse();
+
+    const raw_result = try pugz.render(allocator, doc, data);
+    const result = std.mem.trimRight(u8, raw_result, "\n");
+
+    try std.testing.expectEqualStrings(expected, result);
+}