fix: keep GNOME screencast portal working on Niri

[aethctl]

What changed

fixed portal for screen recording on niri

Area

How it was tested

user applied the fix and screen rec worked instantly afterwards

Checklist

• One logical change, with a clear [area] scope: summary commit subject.
• Matching CHANGELOG.md updated in the area I touched.
• The git hooks pass locally; I did not use --no-verify.
• Lua parses (luac -p), shell scripts pass bash -n, and QML passes
  qmllint where applicable.
• No duplicated config, no dead code, no commented-out code, no em-dash.
• Docs updated if behavior or layout changed.

[feelyourwarmth]

lmk