[Feat]: As a VS Code user, I want the extension's core operations in the Command Palette so that I can create and export diagrams without digging through menus

[emaarco]

Summary

As a VS Code user of the Team Topologies Modeler, I want the extension's core operations —
creating a diagram and exporting the current diagram — available as first-class Command
Palette commands under one shared "Team Topologies" category, so that I can reach them from
Cmd/Ctrl+Shift+P without knowing about the in-canvas menu.

Motivation

The Command Palette is the primary discovery surface in VS Code. Today only the create operations
are palette commands; the export operations live solely inside the webview's collapsed
(Excalidraw-style) menu, so a new user who wants an SVG/PNG has no way to discover them from the
palette, and they can't be bound to a keyboard shortcut. Consolidating the core operations under the
existing Team Topologies category makes the extension self-describing and keyboard-friendly.

What exists today — declared in apps/vscode/package.json → contributes.commands, each with
category: "Team Topologies". There is no contributes.menus.commandPalette restriction, so all
three are already reachable from the palette:

Command id	Title	In palette?	In file/newFile?
teamTopologies.newDiagram	New Empty Diagram	✅	✅
teamTopologies.newFromExample	New Diagram from Example	✅	❌
teamTopologies.newPngDiagram	New Empty Diagram (embedded PNG)	✅	✅

What's missing — core operations that are NOT exposed as commands:

Operation	Today	Proposed command id
Export current diagram as SVG	webview menu only	teamTopologies.exportSvg
Export current diagram as PNG	webview menu only	teamTopologies.exportPng
(secondary) New Diagram from Example in File ▸ New File…	palette only	add to file/newFile menu

Proposed Solution

1. Add two new commands under the shared Team Topologies category:

   • teamTopologies.exportSvg — "Export as SVG"
   • teamTopologies.exportPng — "Export as PNG"

2. Reuse existing logic, don't duplicate. The write-to-disk half already exists in
   apps/vscode/src/exportImage.ts (exportImageToFile), and the webview already emits an export
   protocol message with the rendered data (apps/vscode/src/protocol.ts, handled in
   TtEditorProvider.ts:66 and TtPngEditorProvider.ts:160). The new commands should:

   • resolve the active Team Topologies editor,
   • send a new host → webview "request export" message so the webview produces the SVG text /
     base64 PNG (the same data it already produces for the in-canvas menu),
   • pipe that into the existing exportImageToFile().

   No new export/render code — just a command entry point into the path that already runs.

3. Gate the export commands so they only appear when a diagram editor is focused, via
   contributes.menus.commandPalette with a when clause (e.g.
   activeCustomEditorId == 'teamTopologies.editor' || activeCustomEditorId == 'teamTopologies.pngEditor'),
   so the palette isn't cluttered when no diagram is open.

4. (Secondary) Add teamTopologies.newFromExample to the file/newFile menu for parity with the
   other two create commands.

5. Keep category: "Team Topologies" on every command so they group together in the palette.

Acceptance Criteria

• Team Topologies: Export as SVG and Team Topologies: Export as PNG appear in the Command
  Palette when a .tt / .ttm.json / *.tt.png editor is focused, and are hidden otherwise.
• Running either command produces the same file (with the embedded scene) as the existing
  in-canvas export menu, via exportImageToFile — no duplicated export/render logic.
• All create + export commands share the Team Topologies category in the palette.
• New Diagram from Example is reachable from File ▸ New File… alongside the other create
  commands.
• npm run lint, npm test, and npm run typecheck stay green.

Alternatives Considered

• Leave export in the canvas menu only. Rejected: not discoverable from the palette and can't be
  keybound.
• A single Export… command with a Quick Pick for SVG/PNG. Viable and arguably cleaner; noted as
  an option, but two explicit commands are more directly discoverable and individually keybindable.
• Duplicate the export logic in a command handler. Rejected: violates reuse — exportImageToFile
  plus the existing export protocol message should stay the single source of truth.

[emaarco]

🔗 #40 (Get Started walkthrough) depends on this issue — its walkthrough Step 1 triggers the create command and its export step uses teamTopologies.exportSvg from here. Land this first (at least the command declarations).