Fix CLI publish workflow for nested package

[leehack]

Summary

Fix the mcp_dart_cli publish workflow so nested package releases are published from a clean temporary copy of the repository instead of directly from packages/mcp_dart_cli inside the Git checkout.

The failed mcp_dart_cli-v0.1.7 release produced an effectively empty archive (<1 KB) and pub.dev validation then reported missing pubspec.yaml, LICENSE, README.md, CHANGELOG.md, and bin/mcp_dart.dart. The files were present; dart pub publish was packaging the nested package incorrectly from the Git worktree.

This workflow now preserves normal top-level mcp_dart publishing, while CLI tags copy the repo to $RUNNER_TEMP, remove Git/build/cache metadata, and publish from the copied packages/mcp_dart_cli directory. Keeping the full repo layout preserves the CLI package's existing mcp_dart path override during release validation.

Validation

• Parsed .github/workflows/publish.yml as YAML locally.
• Reproduced the workflow copy approach under /private/tmp.
• Ran dart pub publish --dry-run from the copied packages/mcp_dart_cli directory.
• Verified the dry-run now builds a real 24 KB archive containing the expected package files and reports 0 warnings with only the existing dependency override hint.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.64%. Comparing base (bac25a4) to head (d79cdcd).

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #94   +/-   ##
=======================================
  Coverage   80.64%   80.64%           
=======================================
  Files          43       43           
  Lines        5801     5801           
=======================================
  Hits         4678     4678           
  Misses       1123     1123           

Flag	Coverage Δ
unittests	80.64% <ø> (ø)

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