docs: [torrust#448] add release-new-version agent skill

Author: josecelano

.github/skills/dev/git-workflow/release-new-version/skill.md

@@ -0,0 +1,102 @@
+---
+name: release-new-version
+description: Guide for releasing a new version of the deployer using the standard branch/tag workflow. Covers version bump, signed release commit, pushing main, creating signed tag, creating release branch, and verifying Docker + crate publication workflows. Use when asked to "release", "cut a version", "publish a new version", or "create release vX.Y.Z".
+metadata:
+  author: torrust
+  version: "1.0"
+---
+
+# Release New Version
+
+This skill provides the canonical workflow to release a new version of the Torrust Tracker Deployer.
+
+Primary reference: [`docs/release-process.md`](../../../../../docs/release-process.md)
+
+## Release Order (Mandatory)
+
+Execute these steps in order:
+
+1. Update versions in manifests
+2. Create release commit
+3. Push release commit to `main`
+4. Create and push signed tag `vX.Y.Z`
+5. Create and push release branch `releases/vX.Y.Z`
+6. Verify release workflows
+7. Create GitHub release
+
+Do not reorder these steps.
+
+## Version and Naming Rules
+
+- Git tag: `vX.Y.Z`
+- Release branch: `releases/vX.Y.Z`
+- Docker release tag: `X.Y.Z` (no `v` prefix)
+- Crate version: `X.Y.Z`
+
+## Pre-Flight Checklist
+
+Before starting:
+
+- [ ] Clean working tree (`git status`)
+- [ ] Up to date with `origin/main`
+- [ ] GitHub environment `dockerhub-torrust` configured
+- [ ] GitHub environment `crates-io` configured with `CARGO_REGISTRY_TOKEN`
+- [ ] Releaser has permissions for `main`, tags, and release branches
+
+## Commands
+
+### 1) Update versions
+
+Update `version` in:
+
+- `Cargo.toml`
+- `packages/sdk/Cargo.toml`
+
+### 2) Commit and push
+
+```bash
+git add Cargo.toml packages/sdk/Cargo.toml
+git commit -S -m "release: version vX.Y.Z"
+git push origin main
+```
+
+### 3) Tag and release branch
+
+```bash
+git tag -s -a vX.Y.Z -m "Release vX.Y.Z"
+git push origin vX.Y.Z
+
+git checkout -b releases/vX.Y.Z
+git push origin releases/vX.Y.Z
+```
+
+### 4) Verify workflows
+
+- Container workflow: publishes Docker image from release branch
+- Publish Crate workflow: publishes `torrust-tracker-deployer-sdk`
+
+Workflow files:
+
+- `.github/workflows/container.yaml`
+- `.github/workflows/publish-crate.yaml`
+
+### 5) Create GitHub release
+
+Create the release manually from tag `vX.Y.Z` after both workflows pass.
+
+## Failure Handling
+
+- Docker failed, crate not started: fix Docker workflow and rerun on same release branch
+- Docker passed, crate failed before upload: fix issue and rerun crate workflow on same release branch
+- Crate already published: do not republish same version; cut a patch release
+- Ref already exists (tag/branch): stop and investigate partial release state before continuing
+
+## Quick Validation
+
+```bash
+# Verify refs exist remotely
+git ls-remote --tags origin vX.Y.Z
+git ls-remote --heads origin releases/vX.Y.Z
+```
+
+For full operational guidance, troubleshooting, and rollback/yank policy, use [`docs/release-process.md`](../../../../../docs/release-process.md).

AGENTS.md

@@ -205,6 +205,7 @@ Available skills:
 | Installing system dependencies | `.github/skills/usage/operations/install-system-dependencies/skill.md`       |
 | Organizing Rust modules        | `.github/skills/dev/rust-code-quality/organize-rust-modules/skill.md`        |
 | Placing code in DDD layers     | `.github/skills/dev/rust-code-quality/place-code-in-ddd-layers/skill.md`     |
+| Releasing a new version        | `.github/skills/dev/git-workflow/release-new-version/skill.md`               |
 | Regenerating CLI docs          | `.github/skills/dev/cli/regenerate-cli-docs/skill.md`                        |
 | Rendering tracker artifacts    | `.github/skills/usage/operations/render-tracker-artifacts/skill.md`          |
 | Reviewing pull requests        | `.github/skills/dev/git-workflow/review-pr/skill.md`                         |