Add unbounded-collector warning to the resource collectors page

The warning added to lang_relationships.markdown in #334 also belongs on
the dedicated collectors page, which states that an empty search
expression matches every resource of the type but never cautions
against relying on it.

Closes #389

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Signed-off-by: Michael Harp <mike@mikeharp.com>

Author: miharp

docs/_openvox_8x/lang_collectors.markdown

@@ -53,6 +53,10 @@ resembles the normal syntax for [Puppet expressions][expressions], but is not th
 
 A collector with an empty search expression will match **every** resource of the specified resource type.
 
+{% include alert.html type="warning" content="Do not use unbounded resource collectors without search expressions to limit which resources match.
+They have a side effect of _realizing_ any matching virtual resources whether declared in your own code or in third party modules.
+Using unbounded collectors may result in many unexpected resources being managed and may have catastrophic consequences." %}
+
 Parentheses can be used to improve readability and to modify the priority/grouping of `and`/`or`. You can
 create arbitrarily complex expressions using the following four operators: