Threads: remove xmt tracking parameter from threads.com/threads.net share links

[harusakura924]

Problem

Threads share links include a tracking parameter xmt, e.g.:

https://www.threads.com/@/post/<POST_ID>?xmt=&slof=1

ClearURLs currently does not remove xmt.

Expected

Remove xmt, resulting in a clean URL such as:
https://www.threads.com/@/post/<POST_ID>?slof=1
(or fully clean if slof is also considered a tracking parameter)

Steps to reproduce

1. Open Threads and copy a post link using the share (paper airplane) icon.
2. Observe the generated URL contains xmt=....
3. Run the URL through any tool that consumes ClearURLs rules catalog.
4. xmt remains and is not filtered.

Proposed rule change (data.min.json)

Add a provider for Threads and remove xmt:

"threads": {
  "urlPattern": "^https?:\\/\\/(?:[a-z0-9-]+\\.)*?threads\\.(?:com|net)\\/",
  "completeProvider": false,
  "rules": [
    "xmt"
  ]
}

Notes

• Removing xmt manually does not appear to break navigation (quick test).
• If maintainers confirm slof is tracking-only, it could be added similarly.