Fix m3u-linter CI step to actually lint the real playlist

The config's files list still referenced the README's placeholder
filenames (playlist1.m3u, playlist2.m3u), which don't exist in this
repo, so the linter was silently checking nothing. Point it at the
real playlist.m3u8, drop the noisy full-file cat dump, and surface
its output in the job summary like the iptv-checker step.

.github/workflows/test_playlist.yml

@@ -23,7 +23,7 @@ jobs:
           npm install -g m3u-linter || true
           cat <<EOF > M3u-linter.config.json
             {
-              "files": ["playlist1.m3u", "playlist2.m3u"],
+              "files": ["playlist.m3u8"],
               "rules": {
                 "no-empty-lines": true,
                 "require-header": true,
@@ -38,9 +38,18 @@ jobs:
               }
             }
           EOF
-          ls -lar ./ || true
-          cat playlist.m3u8 || true
-          m3u-linter -c ./M3u-linter.config.json ./playlist.m3u8
+          m3u-linter -c ./M3u-linter.config.json ./playlist.m3u8 | tee m3u-linter-output.txt || true
+
+      - name: Summarize m3u-linter results
+        if: always()
+        run: |
+          {
+            echo "## m3u-linter results"
+            echo ""
+            echo '```'
+            cat m3u-linter-output.txt 2>/dev/null || echo "(no output)"
+            echo '```'
+          } >> "$GITHUB_STEP_SUMMARY"
 
       - name: Install IPTV Checker and check the playlist
         run: |