feat: workflow recipes, eval badges, one-click MCP, playground upgrades, sample gallery, skill-of-the-week

Signature features that turn breadth (174 skills) into a differentiated product:

- Workflow recipes: 5 cross-profession chains (workflows.json) that pass each
  output forward — slash commands (/ship-a-feature etc.), WORKFLOWS.md generated
  by scripts/build-workflows.mjs, README + MCP (list_workflows/get_workflow) wired
- Eval-backed quality: real per-skill scores from evals/results.json surfaced as
  badges in the playground and an honest README section (6 scored skills)
- One-click MCP: 'claude mcp add' install + workflow tools, works in any MCP client
- Playground: 'which skill?' recommender, with/without compare toggle, shareable
  ?skill= deep-links with prefilled inputs
- Sample-output gallery: hand-written examples for the hero five + generator
  (scripts/build-samples.mjs) + web/examples.html
- Skill-of-the-week: scheduled workflow + script that composes X/LinkedIn posts
  and posts to an optional webhook

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.github/workflows/skill-of-the-week.yml

@@ -0,0 +1,42 @@
+name: Skill of the Week
+
+# Picks a featured skill each week, composes X + LinkedIn posts, and (optionally)
+# auto-publishes via a webhook. The post text always lands in the job summary so
+# you can copy-paste even without the webhook configured.
+#
+# To auto-publish: add a repo secret POST_WEBHOOK_URL pointing at a Zapier / Make /
+# Buffer / Slack incoming webhook that takes { text, linkedin, skill, link }.
+
+on:
+  schedule:
+    - cron: '0 9 * * 1' # every Monday 09:00 UTC
+  workflow_dispatch: {}
+
+permissions:
+  contents: write
+
+jobs:
+  feature:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+
+      - name: Pick & compose the skill of the week
+        env:
+          POST_WEBHOOK_URL: ${{ secrets.POST_WEBHOOK_URL }}
+        run: node scripts/skill-of-the-week.mjs
+
+      - name: Commit the featured skill (if it changed)
+        run: |
+          if ! git diff --quiet -- web/skill-of-the-week.json; then
+            git config user.name "github-actions[bot]"
+            git config user.email "github-actions[bot]@users.noreply.github.com"
+            git add web/skill-of-the-week.json
+            git commit -m "chore: skill of the week"
+            git push
+          else
+            echo "No change to web/skill-of-the-week.json"
+          fi