ci: repoint desktop build off the deleted slopsmith org

The slopsmith org was deleted in the DMCA relaunch; core + plugins now
live under the private got-feedback org. Repoint the whole build:

- core clone (nightly.yml, build-common.sh) -> got-feedback/feedback,
  authenticated via GH_CLONE_TOKEN (a PAT with read on the private org;
  threaded through build.yml/nightly.yml/release.yml). Local builds
  without it fall back to the git credential helper.
- bundled-plugin list -> got-feedback/feedback-plugin-*, pruned to the
  set that exists in the org: drops the removed extraction plugins
  (profileimport, tones, sloppak-converter) and not-yet-rehomed ones
  (nam-rig-builder, tabimport); 34 plugins bundled.
- dirname derivation strips the new feedback-plugin- prefix.
- ghcr image -> ghcr.io/got-feedback/feedback; VERSION-sync dispatch
  -> got-feedback/feedback; soundfont + update FEED_URL + docs ->
  got-feedback/feedback-desktop.

Two prerequisites remain (owner-only): set the GH_CLONE_TOKEN secret,
and re-upload the soundfonts-v1 release assets to feedback-desktop.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.github/workflows/build.yml

@@ -147,6 +147,9 @@ jobs:
           # historical default-branch behaviour. clone_slopsmith() in
           # build-common.sh also defaults to main as a second safety net.
           SLOPSMITH_REF: ${{ inputs.slopsmith_ref || 'main' }}
+          # PAT with read access to the private got-feedback repos so
+          # build-common.sh can clone core + the bundled plugins.
+          GH_CLONE_TOKEN: ${{ secrets.SLOPSMITH_SYNC_TOKEN }}
           APPLE_SIGNING_IDENTITY: ${{ secrets.APPLE_SIGNING_IDENTITY }}
           APPLE_ID: ${{ secrets.APPLE_ID }}
           APPLE_APP_SPECIFIC_PASSWORD: ${{ secrets.APPLE_APP_SPECIFIC_PASSWORD }}
@@ -557,7 +560,7 @@ jobs:
             echo "::error::SLOPSMITH_SYNC_TOKEN secret is missing; cannot dispatch."
             exit 1
           fi
-          gh api -X POST repos/slopsmith/slopsmith/dispatches \
+          gh api -X POST repos/got-feedback/feedback/dispatches \
             -f event_type=desktop-released \
             -f "client_payload[version]=$version"
           echo "Dispatched desktop-released event (version=$version) to slopsmith."