ci(release): send User-Agent to crates.io's API

crates.io now returns 403 for API calls without a User-Agent, so
the existing pre-publish "already on crates.io" guard broke: curl -sf
exited non-zero on the 403, the if-then didn't fire, and cargo
publish ran and failed with "crate hm-plugin-protocol@VERSION
already exists" when re-tagging after a partial-success run.

Add -A "harmont-release-ci (github-actions)" to all three guards so
the API returns 200 (exists) or 404 (free) as intended.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: markovejnovic

.github/workflows/release.yml

@@ -41,7 +41,7 @@ jobs:
 
       - name: Publish hm-plugin-protocol
         run: |
-          if curl -sf "https://crates.io/api/v1/crates/hm-plugin-protocol/$VERSION" > /dev/null 2>&1; then
+          if curl -sf -A "harmont-release-ci (github-actions)" "https://crates.io/api/v1/crates/hm-plugin-protocol/$VERSION" > /dev/null 2>&1; then
             echo "hm-plugin-protocol@$VERSION already published, skipping"
           else
             cargo publish -p hm-plugin-protocol --token ${{ secrets.CRATES_IO_TOKEN }} --allow-dirty
@@ -52,7 +52,7 @@ jobs:
 
       - name: Publish hm-plugin-sdk
         run: |
-          if curl -sf "https://crates.io/api/v1/crates/hm-plugin-sdk/$VERSION" > /dev/null 2>&1; then
+          if curl -sf -A "harmont-release-ci (github-actions)" "https://crates.io/api/v1/crates/hm-plugin-sdk/$VERSION" > /dev/null 2>&1; then
             echo "hm-plugin-sdk@$VERSION already published, skipping"
           else
             cargo publish -p hm-plugin-sdk --token ${{ secrets.CRATES_IO_TOKEN }} --allow-dirty
@@ -82,7 +82,7 @@ jobs:
 
       - name: Publish harmont-cli
         run: |
-          if curl -sf "https://crates.io/api/v1/crates/harmont-cli/$VERSION" > /dev/null 2>&1; then
+          if curl -sf -A "harmont-release-ci (github-actions)" "https://crates.io/api/v1/crates/harmont-cli/$VERSION" > /dev/null 2>&1; then
             echo "harmont-cli@$VERSION already published, skipping"
           else
             cargo publish -p harmont-cli --token ${{ secrets.CRATES_IO_TOKEN }} --allow-dirty