feat(cli): mix cert status, measured against a live handshake (T53)

[haiquang9994]

What this adds

mix cert status — the first thing in this repository that measures a padlock rather than
inferring one.

T48 reads an authority off disk, T50 writes a leaf, T51 renders a tls line naming it and T52
replaces it before it expires. Every one of those is a claim about a file. None of them
establishes that the running server presents that file to anything — so the most common TLS fault
of all, a certificate the front end still holds in memory after the file beside it was
replaced, is invisible to all four and obvious to this one.

How it measures

A real TLS handshake to 127.0.0.1:<https_port>, with the site's name as SNI and never a resolved
address — whether blog.test resolves is mix doctor's question, and a handshake that resolved
would report "TLS failed" on a machine whose only fault is a resolver nobody wired.

The verifier is a real WebPkiServerVerifier rooted at this home's authority alone. It records the
genuine verdict and then returns Ok regardless, so that the certificate a failing server
presented can be reported instead of being replaced by an error message about it.

The TLS port is read from stored settings, never through Generator::generate — that method writes
to disk and can reload a running server, which would destroy the exact state this diagnostic exists
to reproduce.

Ordering

CertProblem is first-match-wins, in the order a person would fix things in: NoCertificate ->
NamesDiffer -> NotServed -> ServedCertificateDiffers -> NotTrusted -> Expiring. The CLI
prints the command to run next.

Security

cert.status carries no private key, and a test asserts it. The CA key is not read by any code on
this path.

Testing

• 3 unit tests driving a real rustls server on an OS-chosen port (rule 1: no test claims a port
  number that belongs to the machine it runs on)
• 8 unit tests over the problem-ordering
• 2 CLI integration tests, including one asserting no key material crosses the wire
• 2 #[ignore]d end-to-end tests against a real Caddy, covering the trusted handshake and the
  stale-certificate-in-memory case; both pass on macOS and Windows

Cargo.lock gains 4 lines and zero new packages — rustls and tokio-rustls were already reaching the
daemon through mixengine-core -> reqwest.