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>

examples/samples/executive-update.md

@@ -0,0 +1,26 @@
+---
+skill: executive-update
+title: Executive Update
+input: "Audience: CEO. Period: Q2. Notes: shipped onboarding redesign to all new accounts; activation up sharply; backend hiring two roles behind plan, billing revamp at risk for Q3. Metrics: weekly active accounts, activation rate, NRR."
+source: representative example (hand-written)
+---
+
+# Executive Update — Q2, for the CEO
+
+**Headline:** Activation is up 14 points after the onboarding redesign; we're on track for the Q2 target with one staffing risk to flag for Q3.
+
+## Key metrics
+- **Weekly active accounts:** 12,400 (+18% QoQ)
+- **Activation rate:** 61% (+14 pts) — best quarter on record
+- **Net revenue retention:** 112% (flat)
+
+## Progress
+The redesigned onboarding flow is live for 100% of new accounts. Early cohorts reach value faster — median time-to-value is 2.1 days, down from 4.6.
+
+## Risk & decision needed
+- **Risk:** Backend hiring is two roles behind plan, putting the Q3 billing revamp at risk.
+- **Decision:** Approve contractor budget (~$40k) to hold the Q3 date, or accept a 4-week slip.
+
+## Next steps
+- Roll the activation experiment into the core product (next sprint).
+- Bring a Q3 staffing plan to the next leadership review.