ci(goreleaser): migrate release config to goreleaser v2

goreleaser v1 is EOL; v2 is the current supported major line, so move
the release pipeline over before adding any further release changes.
This is a purely mechanical syntax migration with no behavioral intent
beyond staying on a supported version.

.goreleaser.yaml:
- add top-level `version: 2` (required by goreleaser v2)
- rename `blobs[].folder` to `blobs[].directory`
- rename `snapshot.name_template` to `snapshot.version_template`
- rename `nightly.name_template` to `nightly.version_template`
  (goreleaser-pro only block)

.gitea/workflows/release-tag.yml and release-nightly.yml:
- bump the goreleaser-action `version` pin from `~> v1` to `~> v2`

All other keys (force_token, gitea_urls, builds.no_unique_dist_dir,
checksum.extra_files, signs, release.extra_files, etc.) are valid
as-is under v2 and are left untouched.

`goreleaser check` still reports `DEPRECATED: archives.format should
not be used anymore`. This predates this change and is orthogonal to
the v1->v2 migration, so it is intentionally left unfixed here.

Verified locally with goreleaser v2 OSS (2.11.2):
- `goreleaser check -f .goreleaser.yaml` fails with `field nightly not
  found in type config.Project`, as expected since `nightly` is a
  goreleaser-pro-only key and the local binary is OSS.
- copied the config to a scratch file with the `nightly:` block
  stripped and ran `goreleaser check -f <scratch>` from inside this
  worktree: `configuration is valid, but uses deprecated properties`
  (only the pre-existing archives.format warning). Scratch file was
  deleted afterwards and was never committed.
- using the same scratch file, ran a real build smoke test:
  `SDK_VERSION=$(go list -f '{{.Version}}' -m gitea.dev/sdk) goreleaser
  build --snapshot --clean --single-target -f <scratch>`, which
  succeeded end-to-end including the xz and checksum post hooks;
  `dist/` (git-ignored) was removed afterwards.
- validated .goreleaser.yaml, release-tag.yml and release-nightly.yml
  with python3's yaml.safe_load.

---
Generated by Codet

.gitea/workflows/release-nightly.yml

@@ -28,7 +28,7 @@ jobs:
         uses: goreleaser/goreleaser-action@v7
         with:
             distribution: goreleaser-pro
-            version: "~> v1"
+            version: "~> v2"
             args: release --nightly
         env:
           SDK_VERSION: ${{ steps.sdk_version.outputs.version }}

.gitea/workflows/release-tag.yml

@@ -29,7 +29,7 @@ jobs:
         uses: goreleaser/goreleaser-action@v7
         with:
             distribution: goreleaser-pro
-            version: "~> v1"
+            version: "~> v2"
             args: release
         env:
           SDK_VERSION: ${{ steps.sdk_version.outputs.version }}

.goreleaser.yaml

@@ -1,3 +1,5 @@
+version: 2
+
 before:
   hooks:
     - go mod tidy
@@ -79,7 +81,7 @@ blobs:
     provider: s3
     bucket: "{{ .Env.S3_BUCKET }}"
     region: "{{ .Env.S3_REGION }}"
-    folder: "tea/{{.Version}}"
+    directory: "tea/{{.Version}}"
     extra_files:
       - glob: ./**.xz
       - glob: ./**.sha256
@@ -104,10 +106,10 @@ signs:
     args: ["--batch", "-u", "{{ .Env.GPG_FINGERPRINT }}", "--output", "${signature}", "--detach-sign", "${artifact}"]
 
 snapshot:
-  name_template: "{{ .Branch }}-devel"
+  version_template: "{{ .Branch }}-devel"
 
 nightly:
-  name_template: "{{ .Branch }}"
+  version_template: "{{ .Branch }}"
 
 gitea_urls:
   api: https://gitea.com/api/v1