docker: fix notebook pip-shim drops, first-boot overwrite, base :latest tag, arm64 decord

- pip shim: count editable/local/url/vcs targets (-e ., ., git+https, wheel
  URLs) as install targets, not just canonical package names, so they are no
  longer silently skipped inside notebooks
- notebook sync: never overwrite a pre-existing user notebook on first boot
  (match the refresh path's ownership rule); skip .unsloth_sync_state.tmp when
  recording state so it is not tracked as a managed file
- docker-publish: set flavor latest=false on the base image metadata so a v*
  tag push cannot publish :latest from the base image (the Studio image owns it)
- notebook deps: pin to tested versions and install decord on its own, hard on
  amd64 and fail-soft on arm64 (no aarch64 wheel) so the arm64 base build works

.github/workflows/docker-publish.yml

@@ -232,6 +232,10 @@ jobs:
         uses: docker/metadata-action@v5
         with:
           images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+          # The base image must NEVER claim :latest. metadata-action defaults to
+          # flavor latest=auto, which would tag :latest on a v* (semver) tag push
+          # and collide with the Studio image that legitimately owns :latest.
+          flavor: latest=false
           tags: |
             # The lean training image publishes under the base- prefix; the
             # full Studio image (build-studio/merge-studio below) owns
@@ -437,6 +441,9 @@ jobs:
         uses: docker/metadata-action@v5
         with:
           images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+          # Keep the base image off :latest here too (this recomputes the same
+          # tag list the merge step pushed, so the smoke test pulls the right ref).
+          flavor: latest=false
           tags: |
             type=raw,value=base,enable=${{ github.ref == format('refs/heads/{0}', github.event.repository.default_branch) && github.event.inputs.unsloth_ref == '' }}
             type=ref,event=tag,prefix=base-