ci: consolidate release workflows into a single release.yml

[devin-ai-integration]

Summary

The repo had two workflows triggering on v* tags — the modern release.yml and the legacy upstream release.yaml — which both created draft GitHub releases and built binaries. During the v1.0.2 cut, release.yaml failed:

git checkout -b release/v1.0.2
git push -u origin release/v1.0.2   # ! [rejected] (already exists)

Its "Create release branch" step tries to create release/<version>, which collides whenever a release PR branch already uses that name (as ours did). It also pushes a stray bump version for release commit and produces a second duplicate draft release.

This removes release.yaml and makes release.yml the single source of truth. The only capability release.yaml had that release.yml lacked was the arm64 binary, so release.yml now builds both arches:

-        GOARCH: amd64
-      run: go build ... -o dist/wings_linux_amd64 wings.go
+      run: |
+        for arch in amd64 arm64; do
+          GOARCH="${arch}" go build ... -o "dist/wings_linux_${arch}" wings.go
+        done

checksums.txt now covers both binaries, and the draft release attaches wings_linux_amd64, wings_linux_arm64, and checksums.txt. Release stays draft: true for maintainer review before publishing (unchanged behavior).

No release/<version> branch is created anymore — that pattern was the source of the collision and the stray version-bump commits.

Note

The v1.0.2 release itself is already published (latest) with both binaries + checksums; the container image and Helm chart published successfully. This PR only fixes the workflow for future releases.

Link to Devin session: https://app.devin.ai/sessions/c6e2874ef8924e68a929e491c2018270
Requested by: @Exonical

[devin-ai-integration]

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

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