Fix release workflow's manifest-commit checkout and correct 0.3.0.0 checksum

The "Commit updated manifest to master" step left manifest.json dirty
(modified during the tag checkout by package-release.sh) and then tried to
git checkout master, which git correctly refused -- that's the CI failure
from the v0.3.0.0 tag push. Discard the working-tree manifest.json before
switching branches, matching the /tmp copy-then-restore pattern already used
for carrying the update across.

Also corrects the 0.3.0.0 manifest entry itself: it had been hand-edited
locally with 0.2.0.0's leftover checksum instead of the real zip's hash, and
had dropped the 0.2.0.0 history entry entirely instead of appending. Rebuilt
via update_manifest.py against origin/master's manifest.json using the
actual checksum of the already-uploaded v0.3.0.0 release asset.

.github/workflows/release.yml

@@ -78,6 +78,7 @@ jobs:
           VERSION: ${{ steps.meta.outputs.VERSION }}
         run: |
           cp manifest.json /tmp/manifest.json
+          git checkout -- manifest.json
           git fetch origin master
           git checkout master
           cp /tmp/manifest.json manifest.json

manifest.json

@@ -12,6 +12,14 @@
                 "changelog": "0.3.0.0: SyncPlay stats-for-nerds page and manual one-shot \"sync me to group\" button. No automatic playback intervention. 0.1.0.0: Phase 0 scaffold. Trivial plugin, no functionality yet.",
                 "targetAbi": "10.11.6.0",
                 "sourceUrl": "https://gitea.mrcynic.site/seer/JellyfinSyncPlus/releases/download/v0.3.0.0/JellyfinSyncPlus_0.3.0.0.zip",
+                "checksum": "16b354299e9f6b0900f393045339a93a",
+                "timestamp": "2026-07-10T18:19:38Z"
+            },
+            {
+                "version": "0.2.0.0",
+                "changelog": "0.2.0.0: SyncPlay stats-for-nerds page and manual one-shot \"sync me to group\" button. No automatic playback intervention. 0.1.0.0: Phase 0 scaffold. Trivial plugin, no functionality yet.",
+                "targetAbi": "10.11.6.0",
+                "sourceUrl": "https://gitea.mrcynic.site/seer/JellyfinSyncPlus/releases/download/v0.2.0.0/JellyfinSyncPlus_0.2.0.0.zip",
                 "checksum": "34e384fc5914e2c459f52a9a7bfd91a5",
                 "timestamp": "2026-07-09T15:11:18Z"
             }