feat(lang): a component's event may be called set, a string prop reads a number, one name per component

- An action whose first word is `set` or `emit` followed by `(` is a call, so a component's
  `on set(v: int)` is pressed as `set(4)`; `set x = ...` is still the action.
- A `string` prop (or state, or parameter) given a number in a template reads it as text through
  ludic.ui's new `ui_val_text`; `label="{3}"` used to arrive as "".
- Two components of one name (or of names that differ only in case, which share their functions'
  names) are an error at the second declaration that names the first's file and line, instead of a
  "function cmp_x_def_y is defined twice".

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

selfhost/frontend/component.ludic

@@ -34,6 +34,7 @@ function cm_prefix(name: pointer) -> pointer { return `cmp_{reg_lower(name)}_` }
 function parse_ui_component() -> void {
   pi += 1
   let name = eat_id()
+  cm_unique(name)
   let px = cm_prefix(name)
   g_uses_value = true
   let c = len(g_cm_name)