chore: remove Resend.Cli tool

[felipefreitag]

Remove the internal Resend.Cli tool. The official resend-cli covers the terminal use case. The release zips had zero downloads on the last three releases. Live QA now runs through scratch programs. That does not justify a matching CLI command in every feature PR.

The change deletes tools/Resend.Cli, its solution entries, and its .gitignore lines. cicd/release.sh no longer publishes the self-contained binaries or attaches the zips to the GitHub release. examples/README.md drops the link to the tool. Start with cicd/release.sh and resend-dotnet.sln.

The "Resend CLI" string in Resend.ApiServer stays. It is the mock OAuth grant client name, the value the real API returns. It does not reference this project.

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Summary by cubic

Removes the internal Resend.Cli tool and stops publishing its binaries; the official resend-cli replaces it. No library APIs or runtime behavior change.

• Review focus

  • Start with cicd/release.sh and resend-dotnet.sln: the script no longer builds or attaches CLI artifacts, and the solution no longer references tools/Resend.Cli.
  • Confirm .gitignore and examples/README.md cleanup, and that no remaining references to tools/Resend.Cli exist.
  • The "Resend CLI" string in Resend.ApiServer is intentionally retained as the mock OAuth grant client name.

• Migration

  • If you used the in-repo CLI, install and use the official resend-cli instead.
  • Releases will no longer include CLI zip artifacts.

^{Written for commit 5f8d043. Summary will update on new commits.}

[klotty]

No issues found across 100 files

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

<sub>Auto-approved: This PR removes the redundant internal Resend.Cli tool, its solution entries, and associated build and release artifacts. The core SDK library and its behavior are unaffected.

Re-trigger cubic</sub>