Refactor VS Code language workflows by feature

[Shenglong Li (shenglol)]

Summary

• move decompile, paste-as-Bicep, external-source, and MCP behavior into feature-owned modules with narrow public barrels
• split language protocol and constants ownership across features and infrastructure, and reduce language-client infrastructure to client-wide behavior
• relocate E2E tests and support to the package-level test-e2e directory and update migration progress tracking

Deployment and visualization implementations remain scheduled for the third migration PR; this PR moves only their protocol contracts.

Validation

• npm run lint
• npm run test:unit -- --runInBand (40 tests passed)
• npx tsc --noEmit
• npm run build:e2e
• git diff --check

npm run build:prod was not completed because webpack cannot load the existing .mts configuration under the current Node 22.16.0 environment. The TypeScript phase passes. The E2E runtime suite was not run.

Microsoft Reviewers: Open in CodeFlow

[github-actions]

Test this change out locally with the following install scripts (Action run 31834233793)

VSCode

• Mac/Linux

  bash <(curl -Ls https://aka.ms/bicep/nightly-vsix.sh) --run-id 31834233793

• Windows

  iex "& { $(irm https://aka.ms/bicep/nightly-vsix.ps1) } -RunId 31834233793"

Azure CLI

• Mac/Linux

  bash <(curl -Ls https://aka.ms/bicep/nightly-cli.sh) --run-id 31834233793

• Windows

  iex "& { $(irm https://aka.ms/bicep/nightly-cli.ps1) } -RunId 31834233793"