feat: Implement session Git state management and commit operations

[DonJayamanne]

Fixes #317921

• Added AgentHostSessionGitStateService to manage Git state during agent sessions.
• Integrated Git state probing into AgentService for session lifecycle management.
• Introduced commit operation handling in AgentHostCommitOperationHandler to commit changes and refresh changesets.
• Enhanced AgentService to store authentication tokens for GitHub Copilot.
• Updated tests to cover new commit operation functionality and Git state management.
• Refactored existing code to utilize the new session Git state service and commit operations.

[Copilot]

Pull request overview

This PR adds server-side changeset operations for agent-host sessions, with a commit operation backed by Git state probing and Copilot-generated commit messages.

Changes:

• Extracts session Git state probing into AgentHostSessionGitStateService.
• Adds a changeset operation contribution framework and a commit operation handler/provider.
• Extends agent-host connection interfaces, clients, DI wiring, and tests for the new operation flow.

Show a summary per file

File	Description
src/vs/workbench/services/agentHost/browser/editorRemoteAgentHostServiceClient.ts	Delegates changeset operation invocation through the editor remote client.
src/vs/workbench/contrib/terminal/test/browser/agentHostPty.test.ts	Updates mock agent connection for the new interface method.
src/vs/workbench/contrib/chat/browser/agentSessions/agentHost/loggingAgentConnection.ts	Adds logging wrapper support for changeset operation calls.
src/vs/platform/agentHost/test/node/protocolServerHandler.test.ts	Updates mock agent service for new auth and operation APIs.
src/vs/platform/agentHost/test/node/copilotGitProject.test.ts	Updates Git service test double for new Git methods.
src/vs/platform/agentHost/test/node/copilotAgent.test.ts	Updates Git service test double for new Git methods.
src/vs/platform/agentHost/test/node/agentService.test.ts	Adds token-caching coverage and updates Git service stubs.
src/vs/platform/agentHost/test/node/agentHostCommitOperationProvider.test.ts	Adds coverage for commit operation advertisement logic.
src/vs/platform/agentHost/test/node/agentHostCommitOperationHandler.test.ts	Adds coverage for commit handler success, clean tree, and cancellation paths.
src/vs/platform/agentHost/test/common/sessionTestHelpers.ts	Updates no-op Git service helper for the expanded interface.
src/vs/platform/agentHost/node/protocolServerHandler.ts	Delegates invokeChangesetOperation to AgentService.
src/vs/platform/agentHost/node/agentService.ts	Wires Git state service, operation contributions, token caching, and invocation dispatch.
src/vs/platform/agentHost/node/agentHostSessionGitStateService.ts	Adds dedicated service for session Git state probing and changeset catalogue updates.
src/vs/platform/agentHost/node/agentHostServerMain.ts	Registers IAgentService in server DI scope.
src/vs/platform/agentHost/node/agentHostMain.ts	Registers IAgentService in local agent-host DI scope.
src/vs/platform/agentHost/node/agentHostGitService.ts	Adds Git commit, upstream detection, and push helpers.
src/vs/platform/agentHost/node/agentHostCommitOperationProvider.ts	Adds commit operation contribution for uncommitted changesets.
src/vs/platform/agentHost/node/agentHostCommitOperationHandler.ts	Implements commit operation execution and Copilot commit message generation.
src/vs/platform/agentHost/node/agentHostChangesetOperationContributionService.ts	Adds contribution registry, operation refresh, validation, and dispatch.
src/vs/platform/agentHost/node/agentHostChangesetOperationContributions.ts	Registers default changeset operation contributions.
src/vs/platform/agentHost/electron-browser/localAgentHostService.ts	Delegates local changeset operation invocation.
src/vs/platform/agentHost/common/changesetOperation.ts	Defines common changeset operation contribution interfaces.
src/vs/platform/agentHost/common/agentService.ts	Extends agent service/connection interfaces for auth token retrieval and operation invocation.
src/vs/platform/agentHost/browser/remoteAgentHostProtocolClient.ts	Sends changeset operation requests over JSON-RPC.
src/vs/platform/agentHost/browser/nullAgentHostService.ts	Adds unsupported stub for changeset operation invocation.

Copilot's findings

• Files reviewed: 25/25 changed files
• Comments generated: 3

[Copilot]

Copilot's findings

• Files reviewed: 25/25 changed files
• Comments generated: 1

[vs-code-engineering]

📬 CODENOTIFY

The following users are being notified based on files changed in this PR:

@anthonykim1

Matched files:

• src/vs/workbench/contrib/terminal/test/browser/agentHostPty.test.ts

[connor4312]

We can probably make this @Injectable and have consumers use this rather than adding stuff to the big agentService

[DonJayamanne]

Will fix,