fix: add scoped error logging for lexer/parser errors

- Add std.log.scoped(.pugz) to template.zig and view_engine.zig
- Log detailed error info (code, line, column, message) when parsing fails
- Log template path context in ViewEngine on parse errors
- Remove debug print from lexer, use proper scoped logging instead
- Move benchmarks, docs, examples, playground, tests out of src/ to project root
- Update build.zig and documentation paths accordingly
- Bump version to 0.3.1

examples/demo/build.zig

@@ -0,0 +1,42 @@
+const std = @import("std");
+
+pub fn build(b: *std.Build) void {
+    const target = b.standardTargetOptions(.{});
+    const optimize = b.standardOptimizeOption(.{});
+
+    // Get dependencies
+    const pugz_dep = b.dependency("pugz", .{
+        .target = target,
+        .optimize = optimize,
+    });
+    const httpz_dep = b.dependency("httpz", .{
+        .target = target,
+        .optimize = optimize,
+    });
+
+    // Main executable
+    const exe = b.addExecutable(.{
+        .name = "demo",
+        .root_module = b.createModule(.{
+            .root_source_file = b.path("src/main.zig"),
+            .target = target,
+            .optimize = optimize,
+            .imports = &.{
+                .{ .name = "pugz", .module = pugz_dep.module("pugz") },
+                .{ .name = "httpz", .module = httpz_dep.module("httpz") },
+            },
+        }),
+    });
+
+    b.installArtifact(exe);
+
+    const run_cmd = b.addRunArtifact(exe);
+    run_cmd.step.dependOn(b.getInstallStep());
+
+    if (b.args) |args| {
+        run_cmd.addArgs(args);
+    }
+
+    const run_step = b.step("run", "Run the demo server");
+    run_step.dependOn(&run_cmd.step);
+}