fix: flush static buffer in conditionals and correct helpers import path

- Flush static buffer at end of each conditional branch (if/else/else-if)
  to ensure content is rendered inside the correct blocks
- Add helpers_path parameter to zig_codegen.generate() for correct
  relative imports in nested directories (e.g., '../helpers.zig')
- Fix build.zig to use correct CLI path (src/tpl_compiler/main.zig)
- Export zig_codegen from root.zig for CLI module usage

Bump version to 0.3.11

examples/demo/views/mixins/alerts.pug

@@ -1,12 +1,9 @@
-//- Alert/notification mixins
+mixin alert(alert_messgae)
+  div.alert(role="alert" class!=attributes.class)
+    svg(xmlns="http://www.w3.org/2000/svg" class="h-6 w-6 shrink-0 stroke-current" fill="none" viewBox="0 0 24 24")
+      path(stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M10 14l2-2m0 0l2-2m-2 2l-2-2m2 2l2 2m7-2a9 9 0 11-18 0 9 9 0 0118 0z")
+    span= alert_messgae
 
-mixin alert(message, type)
-  - var alertClass = type ? "alert alert-" + type : "alert alert-info"
-  .alert(class=alertClass)
-    p= message
 
-mixin alert-dismissible(message, type)
-  - var alertClass = type ? "alert alert-" + type : "alert alert-info"
-  .alert.alert-dismissible(class=alertClass)
-    p= message
-    button.alert-close(type="button" aria-label="Close") x
+mixin alert_error(alert_messgae)
+  +alert(alert_messgae)(class="alert-error")