Improve emulator connection failure message

[mkrueger]

Improves the failure message when connect to a local Cosmos DB emulator endpoint fails.

Before:

Failed to connect to the Cosmos DB account.

After (HTTPS attempt):

Could not reach the Cosmos DB emulator at https://localhost:8081/.
Make sure the emulator is running and reachable.
If the protocol is wrong, try http://localhost:8081/ (the Linux emulator defaults to HTTP).
The emulator container's protocol is set with --protocol [https|http].
See: https://learn.microsoft.com/en-us/azure/cosmos-db/emulator-linux

The suggested alternate URL flips the scheme so the user can copy-paste it.

Fixes #74

[Copilot]

Pull request overview

This PR improves the user-facing error message shown when connecting to a local Cosmos DB emulator endpoint fails, providing actionable guidance (including a copy/paste alternate URL with the flipped scheme) to reduce confusion around HTTP vs HTTPS emulator setups.

Changes:

• Adds a new localized error string (error-emulator_connection_failed) with emulator-specific troubleshooting guidance.
• Updates ShellInterpreter.ConnectAsync to throw the emulator-specific message when an emulator connection attempt fails.
• Adds unit tests validating the generated emulator failure message content and scheme-flip suggestion.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
CosmosDBShell/lang/en.ftl	Adds a new localized emulator-specific connection failure message with endpoint/alternate placeholders.
CosmosDBShell/Azure.Data.Cosmos.Shell.Core/ShellInterpreter.cs	Routes emulator connection failures to a new message generator and adds URI scheme-flip helper.
CosmosDBShell.Tests/CommandTests/ConnectCommandTests.cs	Adds tests asserting the emulator failure message includes key guidance and the correct alternate URL.