test: add coverage for MCP tools list and upload tool execute dispatch

[Copilot]

Closes test gaps from the gap-finder report: the MCP tools/list integration test asserted only 5 of ~20 registered tools (missing both upload tools), and the execute-dispatch arms for upload-workitem-attachment and upload-build-attachment had zero direct coverage.

Summary

• tests/mcp_http_tests.rs — extend test_mcp_initialize_and_tools_list with asserts for upload-workitem-attachment and upload-build-attachment so a broken MCP registration on either tool fails the suite.
• src/execute.rs — add 4 unit tests mirroring the existing update-wiki-page / comment-on-work-item patterns to exercise the dispatch arms:
  • test_execute_malformed_upload_workitem_attachment_returns_err
  • test_execute_upload_workitem_attachment_missing_context
  • test_execute_malformed_upload_build_attachment_returns_err
  • test_execute_upload_build_attachment_missing_context
• Resolved a merge conflict with main in tests/mcp_http_tests.rs where main added an upload-pipeline-artifact assertion in the same block; kept all three upload assertions (upload-workitem-attachment, upload-build-attachment, upload-pipeline-artifact).

Note: the issue refers to upload-build-artifact, but the actually-registered tool name is upload-build-attachment (see src/mcp.rs:994, src/execute.rs:352). Tests use the real name.

Test plan

• cargo test --bin ado-aw execute::tests::test_execute_malformed_upload → 2 passed
• cargo test --bin ado-aw execute::tests::test_execute_upload → 2 passed (missing_context)
• cargo test --test mcp_http_tests test_mcp_initialize_and_tools_list → passed (after merge with main)
• cargo test --bin ado-aw execute::tests::test_execute_ → all 24 execute tests passed after merge

[jamesadevine]

@copilot resolve the merge conflicts in this pull request

[Copilot]

@copilot resolve the merge conflicts in this pull request

Resolved in fb39d59. The conflict was in tests/mcp_http_tests.rs where main added an upload-pipeline-artifact assertion in the same block; kept all three (upload-workitem-attachment, upload-build-attachment, upload-pipeline-artifact). Tests pass.