Add Discard changes button to the Agent Changes view

[anderson-joyle]

Summary

Adds a Discard changes button to the Agent Changes view and restores selected local changes to their last-synced baseline through a local-only, projection-aware Sync/LSP operation.

This replacement branch is based on the latest main and supersedes #349.

Resolves #343.

Behavior

• Enables discard only when local changes exist and no sync operation is running.
• Recomputes local changes from disk before discard instead of trusting stale tree state.
• Keeps workspace tracking active when the initial local-diff request fails, allowing later file events to retry.
• Deletes locally created files and restores updated or deleted text resources from the cached cloud baseline.
• Preserves directory-based component-collection references through a durable hidden baseline maintained across clone, pull, push, sync, and retarget flows.
• Removes invalid replacement reference entries when restoring the authoritative manifest.
• Deletes created knowledge attachment metadata and payload atomically, rolling metadata back if payload deletion fails.
• Reports partial outcomes whenever skipped or residual local changes remain; success is shown only when the workspace is clean.
• Returns remaining local changes from the LSP request and refreshes the Agent Changes tree directly.

Design

• WorkspaceSynchronizer.DiscardLocalChanges owns cache restoration and projection-aware file handling in the shared Sync layer.
• powerplatformls/discardLocalChanges combines fresh disk projection with compiled component-collection state before applying discard.
• Local change calculation remains credential-free and does not require Dataverse access.
• The TypeScript command handles orchestration, confirmation, progress, telemetry-safe reporting, and tree replacement.

Testing

• CopilotStudio.Sync unit tests: 525 passed / 0 failed
• Extension host tests: 159 passed / 0 failed
• TypeScript type-check and ESLint: passed
• Discard LSP endpoint regression: passed

[Copilot]

Pull request overview

Adds an end-to-end Discard changes capability to the VS Code extension’s Agent Changes view by introducing a new local-only LSP endpoint backed by projection-aware logic in CopilotStudio.Sync, enabling offline restoration of last-synced baselines.

Changes:

• Adds a Discard changes UI command (title bar + command palette) and orchestration in the extension.
• Introduces powerplatformls/discardLocalChanges and Sync-layer discard APIs/results to revert local changes from the cached baseline.
• Makes local-diff calculation credential-free and adds unit/host test coverage for the new flows.

Reviewed changes

Copilot reviewed 21 out of 21 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/vscode-extensions/microsoft-powerplatformlang-extension/package.json	Contributes the new Discard command to the Agent Changes view and command list.
src/vscode-extensions/microsoft-powerplatformlang-extension/client/src/types.ts	Adds Discard result contracts and simplifies DiffRequest for credential-free local diff.
src/vscode-extensions/microsoft-powerplatformlang-extension/client/src/tests/host/workspaceScm.test.ts	Adds host-test coverage for initial local diff failure handling.
src/vscode-extensions/microsoft-powerplatformlang-extension/client/src/tests/host/discardChanges.test.ts	Adds host-test coverage for discard telemetry formatting and completeness logic.
src/vscode-extensions/microsoft-powerplatformlang-extension/client/src/sync/workspaceScm.ts	Adds local-change replacement support and adjusts local diff fetching/initial error handling.
src/vscode-extensions/microsoft-powerplatformlang-extension/client/src/extension.ts	Registers the new Discard Changes command at activation.
src/vscode-extensions/microsoft-powerplatformlang-extension/client/src/constants.ts	Adds the new LSP method name constant for discard.
src/vscode-extensions/microsoft-powerplatformlang-extension/client/src/commands/discardChanges.ts	Implements the Discard Changes command UX + LSP invocation + reporting.
src/LanguageServers/PowerPlatformLS/UnitTests/PowerPlatformLS.UnitTests/Impl.PullAgent/Methods/ReattachAgentHandlerTests.cs	Updates test doubles for new synchronizer API surface.
src/LanguageServers/PowerPlatformLS/UnitTests/PowerPlatformLS.UnitTests/Impl.PullAgent/Methods/DiscardLocalChangesHandlerTests.cs	Adds unit tests for the new discard handler behavior.
src/LanguageServers/PowerPlatformLS/UnitTests/PowerPlatformLS.UnitTests/Impl.PullAgent/AgentWriterTests.cs	Updates local-change tests to use the new credential-free local diff API.
src/LanguageServers/PowerPlatformLS/UnitTests/PowerPlatformLS.UnitTests/Impl.Core/ChangeMethodTests.cs	Adds regression coverage for discarding local changes without remote credentials.
src/LanguageServers/PowerPlatformLS/Impl.PullAgent/GetLocalChangeHandler.cs	Removes Dataverse/token dependencies from local diff handling.
src/LanguageServers/PowerPlatformLS/Impl.PullAgent/DiscardLocalChangesHandler.cs	Adds the new local-only discard endpoint and response shaping.
src/LanguageServers/PowerPlatformLS/Impl.PullAgent/DiffLocalRequest.cs	Simplifies the local diff request contract to workspace-only.
src/LanguageServers/PowerPlatformLS/Impl.PullAgent/DependencyInjection/PullAgentLspModule.cs	Registers the new discard handler in DI.
src/LanguageServers/PowerPlatformLS/Contracts.Internal/Constants.cs	Adds the JSON-RPC method constant for discard and confirms camelCase serialization.
src/CopilotStudio.Sync/WorkspaceSynchronizer.cs	Implements projection-aware discard logic and adds a durable references baseline cache.
src/CopilotStudio.Sync/Models.cs	Adds DiscardResult and DiscardSkippedChange models for the new API.
src/CopilotStudio.Sync/IWorkspaceSynchronizer.cs	Adds discard APIs and a new local-diff overload without remote-service dependencies.
src/CopilotStudio.Sync.UnitTests/DiscardLocalChangesTests.cs	Adds extensive Sync-layer unit tests for discard scenarios and partial-failure behavior.

Comments suppressed due to low confidence (1)

src/vscode-extensions/microsoft-powerplatformlang-extension/client/src/sync/workspaceScm.ts:345

• onLocalChange logs the failure and then rethrows. Because onWorkspaceChange already has its own .catch(...) logging, this change causes duplicate telemetry/log entries for the same local-diff failure and makes initial SCM setup rely on the separate refreshInitialLocalChanges swallow wrapper to avoid aborting setup. Consider logging once and not rethrowing from onLocalChange so tracking stays alive without double-reporting.

      } catch (e) {
        logger.logError(TelemetryEventsKeys.SyncWorkspaceError, undefined, {
          message: `onLocalChangeError: ${e instanceof Error ? e.message : String(e)}`
        });
        throw e;