Restructure Step 0 welcome with demo-first value hook and path-based navigation

[Copilot]

Step 0 had the highest workshop dropout and was losing skeptical/impatient beginners before any technical work. The welcome needed to show concrete end-state value immediately and give faster navigation for different learner intents.

• Demo-first opening (within first 10 lines)

  • Moved the finished-artifact preview to the top of workshop/00-welcome.md.
  • Front-loaded the completed workflow run visual and the generated daily status output visual.

• Audience-specific value framing

  • Added a “Why this matters in 60 seconds” section with targeted value bullets for:
    • personal learners
    • work-project engineers
    • team evaluators

• Path-based navigation

  • Added a “Choose your path” callout with direct jumps:
    • brand-new to GitHub → Step 1
    • already knows GitHub Actions → Step 5
    • wants final workflow only → Step 11

• Orientation content preserved and reorganized

  • Kept existing orientation sections, moving them below the new hook.
  • Reworded the legacy fast-path tip to avoid duplicating the new chooser block.

> [!TIP]
> **Choose your path**
> - **I'm brand new to GitHub** → Start at [Step 1: What You Need Before We Start](01-prerequisites.md) and follow every step in order.
> - **I know GitHub Actions** → Jump to [Step 5: What Are Agentic Workflows?](05-agentic-workflows-intro.md).
> - **I just want to see the final workflow** → Go straight to [Step 11: Build the Daily Status Workflow](11-build-daily-status.md).