carlos / platform Public

What: carlos email test now sends multipart/alternative, a text/plain part followed by a text/html part, instead of plain text only.

Why: James wanted to be sure apps can send multipart (plain + HTML) mail through the platform. They already can. The delivered credential is SES SMTP submission authorised by ses:SendRawEmail (internal/mail/policy.go), and the only policy condition is ses:FromAddress. Nothing on the platform reads or rewrites a body. But the one message the platform builds itself was plain text, so email test could not show it.

Changes:

• mail_cli.go: buildTestMessage builds the body with mime/multipart and adds MIME-Version and the multipart Content-Type.
• mail_cli_test.go: TestBuildTestMessageIsMultipartAlternative parses the message with net/mail + mime/multipart, checks both parts in plain-then-HTML order, and checks no line exceeds 998 bytes.
• docs/site/cli.md: says the test message is multipart, and that apps may send any MIME message over their credential.

Tested: gofmt/vet clean, go build ./..., full root package and internal/docsite tests pass locally. No live carlos email test was run.