ci: package skill as installable zip via Gitea Actions

Add a reproducible way to build the Claude-skill package and publish it:

- scripts/build-skill-zip.sh: stages SKILL.md + README + references/ + assets/
  into a zip whose single top-level cycling-training/ folder is the layout
  Claude Desktop / claude.ai import expects. Validates SKILL.md frontmatter.
- .gitea/workflows/release-skill.yml: on tag v* builds the zip and attaches it
  to a Gitea release (via the API using the automatic token); on manual
  dispatch uploads it as a run artifact.
- README: document the packaging/release flow and Claude Desktop zip-import.
- .gitignore: ignore dist/ build output.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TqrhBhC3GEcKyaw8RTk8G6

README.md

@@ -64,11 +64,35 @@ git clone <this-repo> .claude/skills/cycling-training
 Claude auto-discovers any `SKILL.md` under a `skills/` directory. The `description` field in the
 frontmatter is what Claude matches against to decide when to load the skill, so keep it intact.
 
-**Claude.ai / Claude Desktop:** upload or sync the folder as a skill per the current skills UI.
+**Claude Desktop / claude.ai (import a zip):** the skill ships as a packaged `.zip` whose single
+top-level `cycling-training/` folder holds `SKILL.md` and the docs — the layout Claude expects. Get
+the zip one of two ways, then import it in **Settings → Skills**:
+
+- **From a release:** download `cycling-training-<version>.zip` from the repo's Releases (produced
+  automatically — see *Packaging & releases* below).
+- **Build it yourself:**
+  ```bash
+  scripts/build-skill-zip.sh v1.0.0   # -> dist/cycling-training-v1.0.0.zip
+  ```
 
 Once installed, this skill loads automatically when you ask cycling-training questions, and it
 pairs with your connected Intervals.icu MCP server for the live data.
 
+## Packaging & releases
+
+`scripts/build-skill-zip.sh [version]` stages the installable files and produces
+`dist/cycling-training-<version>.zip` (validating that `SKILL.md` carries `name`/`description`
+frontmatter). A Gitea Actions workflow, `.gitea/workflows/release-skill.yml`, runs it:
+
+- **Push a tag `v*`** (e.g. `git tag v1.0.0 && git push origin v1.0.0`) → builds the zip and
+  **attaches it to a Gitea release** for that tag.
+- **Run the workflow manually** (workflow_dispatch) → builds the zip and uploads it as a run
+  artifact you can download.
+
+The workflow needs a registered Actions runner, Actions enabled for the repo, and the automatic
+`GITHUB_TOKEN` to have `contents:write` (granted via the workflow's `permissions` block on
+Gitea ≥ 1.20).
+
 ## How to read the docs
 
 - **`SKILL.md` is a router, not a manual.** It points to the one reference doc that answers the