fix(release): make package-channel docs truthful

Closes #944\n\n## Summary\n- mark Docker/GHCR publishing as experimental while the package is not publicly readable\n- align installer and release docs with the live npm/Scoop state\n- keep package-channel verification explicit for release triage\n\n## Test plan\n- ruby -e 'require "yaml"; YAML.load_file(".github/workflows/release.yml"); puts "release.yml ok"'\n- cargo test -p deepseek-tui-cli update::tests::test_asset_matching_accepts_binary_assets_and_rejects_checksums --locked\n- cargo fmt --all -- --check\n- git diff --check origin/main...HEAD\n- CI: Version drift, Lint, Test (ubuntu-latest), Test (macos-latest), Test (windows-latest), npm wrapper smoke

.github/workflows/release.yml

@@ -139,6 +139,10 @@ jobs:
   docker:
     needs: build
     if: ${{ !cancelled() && needs.build.result == 'success' }}
+    # Docker/GHCR is experimental and not a supported release channel yet.
+    # Keep binary GitHub Releases publishable while the arm64 image build path
+    # is hardened separately.
+    continue-on-error: true
     runs-on: ubuntu-latest
     permissions:
       contents: read