Render Modal as real markup; drain scripts via CaptureScript (#2742)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>

shared/lib/include-args.ts

@@ -1,10 +1,7 @@
 /**
- * Reproduces the LiquidJS `include['x']` meta-property bug: when a param isn't
- * explicitly passed, referencing it as a bare property (rather than a lookup)
- * falls back to the include's argument COUNT instead of undefined. Some ported
- * components (ui/spinner.html, ui/nav-segmented.html) rely on this to emit
- * "junk" classes like `spinner-border-2` / `nav-2` that the DOM parity diff
- * does not strip, so they must be reproduced verbatim.
+ * Returns how many of the given prop keys are explicitly set (not undefined).
+ * Some components use this count as a class suffix when `size` (or similar) is
+ * omitted, e.g. `spinner-border-2` or `nav-2`.
  */
 export function includeArgCount(props: Record<string, unknown>, keys: readonly string[]): number {
   return keys.filter((k) => props[k] !== undefined).length