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

.gitea/workflows/release-skill.yml

@@ -0,0 +1,90 @@
+name: Package skill
+
+# Builds the installable Claude-skill zip (dist/cycling-training-<version>.zip).
+#
+#   - Push a tag  v*   -> builds the zip AND attaches it to a Gitea release.
+#   - Run manually     -> builds the zip and uploads it as a run artifact.
+#
+# Requirements on the Gitea side:
+#   * A registered Actions runner (image with bash/zip/curl, e.g. catthehacker/ubuntu).
+#   * Actions enabled for this repo (Settings > Actions).
+#   * The automatic ${{ secrets.GITHUB_TOKEN }} must have contents:write so the
+#     release step can create the release / upload the asset (granted via the
+#     `permissions` block below on Gitea >= 1.20).
+
+on:
+  push:
+    tags:
+      - 'v*'
+  workflow_dispatch:
+    inputs:
+      version:
+        description: 'Version label for the zip (e.g. v1.0.0)'
+        required: false
+        default: 'manual'
+
+jobs:
+  package:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Determine version
+        id: ver
+        run: |
+          if [ "${{ github.ref_type }}" = "tag" ]; then
+            echo "version=${{ github.ref_name }}" >> "$GITHUB_OUTPUT"
+          else
+            echo "version=${{ github.event.inputs.version }}" >> "$GITHUB_OUTPUT"
+          fi
+
+      - name: Build skill zip
+        run: bash scripts/build-skill-zip.sh "${{ steps.ver.outputs.version }}"
+
+      - name: Upload run artifact
+        uses: actions/upload-artifact@v3
+        with:
+          name: cycling-training-skill-${{ steps.ver.outputs.version }}
+          path: dist/*.zip
+          if-no-files-found: error
+
+      - name: Attach zip to release
+        if: github.ref_type == 'tag'
+        env:
+          TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          SERVER: ${{ github.server_url }}
+          REPO: ${{ github.repository }}
+          VERSION: ${{ steps.ver.outputs.version }}
+        run: |
+          set -euo pipefail
+          ZIP="$(ls dist/*.zip | head -1)"
+          echo "Publishing ${ZIP} to ${SERVER}/${REPO} release ${VERSION}"
+
+          # Create the release for this tag; if it already exists, look up its id.
+          REL_ID="$(curl -sS -X POST \
+            -H "Authorization: token ${TOKEN}" \
+            -H "Content-Type: application/json" \
+            "${SERVER}/api/v1/repos/${REPO}/releases" \
+            -d "{\"tag_name\":\"${VERSION}\",\"name\":\"${VERSION}\",\"body\":\"Installable Claude-skill package for cycling-training. Download the .zip below and import it in Claude Desktop / claude.ai (Settings > Skills) or unzip into your Claude Code skills directory.\"}" \
+            | grep -o '"id":[0-9]*' | head -1 | cut -d: -f2 || true)"
+
+          if [ -z "${REL_ID}" ]; then
+            REL_ID="$(curl -sS \
+              -H "Authorization: token ${TOKEN}" \
+              "${SERVER}/api/v1/repos/${REPO}/releases/tags/${VERSION}" \
+              | grep -o '"id":[0-9]*' | head -1 | cut -d: -f2)"
+          fi
+
+          if [ -z "${REL_ID}" ]; then
+            echo "ERROR: could not create or find a release for tag ${VERSION}" >&2
+            exit 1
+          fi
+
+          curl -sS -X POST \
+            -H "Authorization: token ${TOKEN}" \
+            -F "attachment=@${ZIP}" \
+            "${SERVER}/api/v1/repos/${REPO}/releases/${REL_ID}/assets?name=$(basename "${ZIP}")"
+          echo "Attached $(basename "${ZIP}") to release ${VERSION} (id ${REL_ID})."