[Feat]: As a first-time user, I want a guided walkthrough so that I can create and export my first Wardley Map within minutes

[emaarco]

Depends on: #63 (Command Palette operations — shared Wardley category create command + new wardley.exportSvg command).

Summary

As a first-time user, I want a single VS Code walkthrough (contributes.walkthroughs) that takes
me from a freshly-installed extension to my first exported Wardley Map, following the
official walkthrough UX guidelines.

Motivation

The extension contributes no walkthrough, so after install there is no in-editor onboarding: a
new user must already know the file extensions, the two custom editors, and the canvas toolbar. A
focused walkthrough on VS Code's Get Started page shortens time-to-first-map and teaches the
graphical ↔ OWM-DSL round-trip and export. Per the guidelines, this should be one walkthrough
with a small number of steps, each with a verb action button and theme-aware SVG media.

Proposed Solution

Add one walkthrough — id: wardley.gettingStarted, title "Get Started with Wardley Maps" —
with 3 focused steps. Each step has a single verb action button, theme-aware SVG media
(apps/vscode/media/walkthroughs/*.svg, using VS Code Theme Colors so it renders in light & dark,
with altText), and a realistic completionEvents:

1. Create your first map — description links
   [Create Example Map](command:wardley.newMapFromExample) (opens the Tea Shop example — an ideal
   first artifact). completionEvents: ["onCommand:wardley.newMapFromExample"].
   → Dependency: this is the "create a model" command from Issue A ([Feat]: As a VS Code user, I want the extension's core operations in the Command Palette so that I can create and export maps without digging through menus #63). It already exists today
   (wardley.newMapFromExample), so the step is not blocked; Issue A ([Feat]: As a VS Code user, I want the extension's core operations in the Command Palette so that I can create and export maps without digging through menus #63) canonicalizes its
   category/title.
2. Edit visually — and in text — explain the lossless graphical ↔ OWM-DSL round-trip; button
   [Browse Wardley Commands](command:workbench.action.quickOpen?%5B%22%3EWardley%20%22%5D) prefills
   the palette with >Wardley to reveal the command surface from Issue A ([Feat]: As a VS Code user, I want the extension's core operations in the Command Palette so that I can create and export maps without digging through menus #63).
   completionEvents: ["onCommand:workbench.action.quickOpen"].
3. Export to share — button [Export as SVG](command:wardley.exportSvg) to export the map for
   sharing/embedding. completionEvents: ["onCommand:wardley.exportSvg"].
   → Dependency: requires the new wardley.exportSvg command from Issue A ([Feat]: As a VS Code user, I want the extension's core operations in the Command Palette so that I can create and export maps without digging through menus #63) → this step is
   blocked by Issue A ([Feat]: As a VS Code user, I want the extension's core operations in the Command Palette so that I can create and export maps without digging through menus #63).

Acceptance Criteria

• Exactly one walkthrough (contributes.walkthroughs, id wardley.gettingStarted) is shown
  on the Get Started page after install.
• 3 steps (≤ 4), each with a single verb action button.
• Media are theme-aware SVGs with altText (render correctly in light and dark themes).
• completionEvents check off each step when its action runs (onCommand:…).
• Step 1 triggers the create command (wardley.newMapFromExample) from Issue A ([Feat]: As a VS Code user, I want the extension's core operations in the Command Palette so that I can create and export maps without digging through menus #63)'s shared category.
• Step 3 triggers wardley.exportSvg (depends on Issue A ([Feat]: As a VS Code user, I want the extension's core operations in the Command Palette so that I can create and export maps without digging through menus #63)).
• No additional walkthroughs are introduced.
• npm run lint, npm test, and npm run typecheck stay green.

Alternatives Considered

• Multiple walkthroughs (e.g. "basics" + "advanced"). Rejected per the guideline "don't add
  multiple walkthroughs unless absolutely necessary".
• README-only getting-started section. Useful, but not surfaced in-editor on first run; the
  walkthrough is the native onboarding surface.
• Screenshot PNG media. Rejected: not theme-aware.

---

Note: uses enhancement + documentation (the repo's docs label); no workspace/scope label exists.

[emaarco]

completed with #65