fix: correct markdownlint errors in existing skill files

- sdlc-diagram.md: remove extra trailing blank line (MD012)
- sdlc/SKILL.md lines 76,91: add language to fenced code blocks (MD040)
- uat/SKILL.md: verify trailing newline (MD047)

These pre-existing issues were surfaced by the expanded CI introduced
in the 'ci: move to .gitea/workflows and expand lint coverage' commit.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

.gitea/workflows/ci.yaml

@@ -0,0 +1,44 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install linters
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y --no-install-recommends shellcheck yamllint
+
+      - name: Lint Markdown
+        uses: DavidAnson/markdownlint-cli2-action@v19
+        with:
+          globs: "**/*.md"
+
+      - name: Lint YAML
+        run: yamllint .
+
+      - name: Shellcheck
+        run: shellcheck scripts/*.sh
+
+      - name: Validate skill frontmatter
+        run: |
+          set -e
+          fail=0
+          for f in skills/*/SKILL.md; do
+            fm=$(awk 'BEGIN{c=0} /^---$/{c++; next} c==1{print} c>=2{exit}' "$f")
+            for key in name description; do
+              if ! printf '%s\n' "$fm" | grep -qE "^${key}:[[:space:]]"; then
+                echo "::error file=${f}::missing '${key}' in YAML frontmatter"
+                fail=1
+              fi
+            done
+          done
+          exit $fail

.github/workflows/ci.yaml

@@ -1,17 +0,0 @@
-name: CI
-
-on:
-  push:
-    branches: [main]
-  pull_request:
-    branches: [main]
-
-jobs:
-  lint:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v4
-      - name: Lint Markdown
-        uses: DavidAnson/markdownlint-cli2-action@v19
-        with:
-          globs: "**/*.md"

.github/workflows/plugin-release.yaml

@@ -437,4 +437,3 @@ jobs:
           echo "All checksums consistent — ArtifactHub will index correctly."
         env:
           GH_TOKEN: ${{ steps.app-token.outputs.token }}
-

.yamllint.yaml

@@ -0,0 +1,7 @@
+extends: default
+
+rules:
+  line-length: disable
+  document-start: disable
+  truthy:
+    check-keys: false

skills/sdlc/SKILL.md

@@ -73,7 +73,7 @@ Each promotion is a PR reviewed and merged by its gate owner:
 
 ### Pipeline A: Plugin/Feature Changes
 
-```
+```text
 Engineer → PR to dev → self-merge → deploys to dev
 → Engineer validates on dev
 → PR from dev → uat → QA reviews → QA merges
@@ -88,7 +88,7 @@ Applies to changes in `headlamp-*-plugin/` repos (plugin code, features, bug fix
 
 ### Pipeline B: Infrastructure Changes (No UI Impact)
 
-```
+```text
 Engineer → PR to main → CI passes → QA reviews → QA merges
 → Production
 ```

skills/sdlc/sdlc-diagram.md

@@ -132,4 +132,3 @@ flowchart LR
     class UATB uat
     class MAIN prod
 ```
-