ci: allow manual GoReleaser dispatch for existing tags

Release Please creates GitHub releases without pushing tag events that
reliably trigger GoReleaser; workflow_dispatch publishes binaries for a
given tag on demand.

Co-authored-by: Cursor <cursoragent@cursor.com>

.github/workflows/release.yml

@@ -3,6 +3,12 @@ name: Release
 on:
   push:
     tags: ["v*"]
+  workflow_dispatch:
+    inputs:
+      tag:
+        description: Git tag to release (e.g. v0.4.0)
+        required: true
+        type: string
 
 permissions:
   contents: write
@@ -15,6 +21,7 @@ jobs:
       - uses: actions/checkout@v4
         with:
           fetch-depth: 0
+          ref: ${{ github.event_name == 'workflow_dispatch' && format('refs/tags/{0}', inputs.tag) || github.ref }}
 
       - name: Set up Go
         uses: actions/setup-go@v5