Wire up LSP data source for visual designer (Migration Step 4)

[shenglol]

Connects the new React-based visual designer to the textDocument/deploymentGraph LSP notification via @vscode-bicep-ui/messaging.

What's included

• Message contract — READY_NOTIFICATION / DEPLOYMENT_GRAPH_NOTIFICATION types in messages.ts
• Data binding — useDeploymentGraph hook maps DeploymentGraph → Jotai atoms with position snapshotting for smooth transitions, empty-module demotion, and :: hierarchy parsing
• Dev mode — FakeMessageChannel + DevToolbar with 5 sample graphs (including a complex VWAN topology) and 11 mutations for testing incremental updates
• Layout — ELK layered auto-layout with persistent centering offset, spring animations, and useFitView
• Visual polish — error borders, Material-inspired dark theme (distinct border/edge colors), collection stacking (isCollection → ghost card), edge z-index under nodes, graph control bar

Microsoft Reviewers: Open in CodeFlow

[github-actions]

Test this change out locally with the following install scripts (Action run 22123461446)

VSCode

• Mac/Linux

  bash <(curl -Ls https://aka.ms/bicep/nightly-vsix.sh) --run-id 22123461446

• Windows

  iex "& { $(irm https://aka.ms/bicep/nightly-vsix.ps1) } -RunId 22123461446"

Azure CLI

• Mac/Linux

  bash <(curl -Ls https://aka.ms/bicep/nightly-cli.sh) --run-id 22123461446

• Windows

  iex "& { $(irm https://aka.ms/bicep/nightly-cli.ps1) } -RunId 22123461446"