Refactor visual designer architecture and graph coordination

[Shenglong Li (shenglol)]

Summary

Refactor the visual designer into explicit app, feature, UI, and library boundaries while preserving its existing behavior.

• add feature-owned, typed messaging APIs
• establish an explicit app environment for the Jotai store, host channel, synchronization, and theme
• scope the canvas runtime to Canvas and expose UI actions through context
• separate the client graph model, layout processing, rendering, and update coordination
• simplify feature composition and consolidate the architecture documentation

Graph update coordinator fixes

The canvas now uses a React-independent GraphUpdateCoordinator with controlled-promise unit tests for its ordering rules. In addition to making the update flow easier to test, it fixes several concurrency bugs:

• Preserve layout retries: a graphChanged layout response now schedules reconciliation and re-pends the interrupted layout, preventing a graph from remaining hidden behind the layout visibility gate.
• Preserve reset intent: Reset Graph Layout outranks automatic layout and retains reset mode across retries, so it cannot be downgraded to an automatic layout that skips unchanged node dimensions.
• Protect resource placement: update responses that arrive during a source mutation are discarded and fetched again after the expected node ID is bound to its drop origin.
• Serialize mutations safely: source mutations run one at a time, and a rejected mutation does not stall the following mutation.
• Settle requests correctly: callers arriving during a pass wait until all coalesced work is complete; failed passes release shared waiters so the reset-layout action cannot remain locked for the rest of the session.
• Avoid lost follow-up work: pending work recorded while a drain is unwinding triggers another drain.

Validation

• visual designer lint
• 62 visual designer unit tests
• 31 Playwright end-to-end tests
• all 5 vscode-bicep-ui workspace builds
• all 4 vscode-bicep-ui workspace test tasks

Microsoft Reviewers: Open in CodeFlow

[github-actions]

Test this change out locally with the following install scripts (Action run 33354576278)

VSCode

• Mac/Linux

  bash <(curl -Ls https://aka.ms/bicep/nightly-vsix.sh) --run-id 33354576278

• Windows

  iex "& { $(irm https://aka.ms/bicep/nightly-vsix.ps1) } -RunId 33354576278"

Azure CLI

• Mac/Linux

  bash <(curl -Ls https://aka.ms/bicep/nightly-cli.sh) --run-id 33354576278

• Windows

  iex "& { $(irm https://aka.ms/bicep/nightly-cli.ps1) } -RunId 33354576278"