fix(opencode-plugin): track active release branch in CI + align combo-id fixture

The opencode-plugin CI workflow trigger was pinned to release/v3.8.2 since
its creation, so it stopped firing once the active release line moved on —
the workflow never ran mid-cycle. Switch push/pull_request branch filters
to release/** so it tracks whatever release branch is active.

Also align the provider.test.ts fixture expectations with the combo-id
contract from #10345/#10821: mapRawModelToModelV2 leaves bare combo ids
(owned_by: "combo") unprefixed so OpenCode's `-m <plugin>/<combo>` lookup
resolves them directly. The two assertions still expected the old
provider-prefixed form.

Closes #11291
Closes #11292

.github/workflows/opencode-plugin-ci.yml

@@ -2,11 +2,11 @@ name: opencode-plugin CI
 
 on:
   push:
-    branches: [main, release/v3.8.2]
+    branches: [main, "release/**"]
     paths:
       - "@omniroute/opencode-plugin/**"
   pull_request:
-    branches: [main, release/v3.8.2]
+    branches: [main, "release/**"]
     paths:
       - "@omniroute/opencode-plugin/**"
     types: [opened, synchronize, reopened, ready_for_review]