[PROTOTYPE] [WIP] REXML for parsing taskoutput tool results

[LasmarKhalifa]

This prototype explores a different way of parsing taskoutput's tool result messages by using REXML. Nokogiri was not a good fit for our case because it uses native dependencies.

The challenges we face are the following:
-Taskoutput's tool result message resembles XML but is not. Special characters such as < are not escaped and there is no shared root.
-Most parsers raise an exception if they hit an unescaped character. This is fine for taskoutput's status and retrieval_status messages as they can only contain one of 3 options each, and neither contains unescaped characters. However, the content of that message includes other fields, such as <output> which can contain unescaped characters. We don't want our implementation to break in those cases.

This PR suggests the implementation of REXML's pull parser, which is a lazy parser. We only parsethe next element if we need to and stop once we have either status or retrieval_status. If at any point we raise, we just return nil.

This works and the main drawback is that it doesn't handle unescaped characters. That's fine for our taskoutput case, but we cannot use this in other places like error_lines

[LasmarKhalifa]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• [PROTOTYPE] [WIP] Regex for parsing taskoutput results #984
• [PROTOTYPE] [WIP] REXML for parsing taskoutput tool results #983 👈 (View in Graphite)
• add taskoutput tool result formatter backed by nokogiri #960
• add task tool result formatter #963
• add agent tool result formatter #962
• add taskcreate tool result formatter #959
• add taskupdate tool result formatter #958
• add todowrite tool result formatter #957
• add skill tool result formatter #956
• add edit tool result formatter #955
• add write tool result formatter #954
• add grep tool result formatter #953
• add glob tool result formatter #952
• add read tool result formatter #951
• add bash tool result formatter #949
• Centralize tool result error handling in format with error_line helper #948
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.