Create shared helper module for tsp-client commands

[samvaity]

Created shared helpers for tsp-client commands (common utility class used by multiple tools) so they provide single implementation of core logic

• Looser coupling (for multiple tool calls to use)
• Clear separation of “UI” (CLI command) vs logic

Will add update workflow in a follow-up PR, which will include details with the TspClientUpdate Tooling (it was increasing the size of PR)

[Copilot]

Pull Request Overview

This PR refactors the TypeSpec conversion tool to use a shared helper module for tsp-client commands. The goal is to create reusable logic that can be shared across multiple tools while maintaining loose coupling between UI commands and core business logic.

• Extracts the tsp-client convert command execution logic into a dedicated helper class
• Introduces dependency injection for the new ITspClientHelper interface
• Updates existing tests to accommodate the new constructor dependencies

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
TspConvertTool.cs	Refactored to use injected ITspClientHelper instead of inline tsp-client execution
ServiceRegistrations.cs	Added DI registration for the new ITspClientHelper interface
TspClientHelper.cs	New implementation class containing the extracted tsp-client convert logic
ITspClientHelper.cs	New interface defining the contract for tsp-client operations
TspConvertToolTest.cs	Updated test constructor calls to include the new dependency

Comments suppressed due to low confidence (1)

tools/azsdk-cli/Azure.Sdk.Tools.Cli/Tools/TypeSpec/TspConvertTool.cs:161

• Duplicate file existence check. Lines 151-155 already perform the same validation with fullPath variable. Remove this redundant check.

            var fullPathToSwaggerReadme = Path.GetFullPath(pathToSwaggerReadme.Trim());
            if (!File.Exists(fullPathToSwaggerReadme))
            {
                return $"Failed: pathToSwaggerReadme '{fullPathToSwaggerReadme}' does not exist.";
            }

[samvaity]

Did a poor rebase