Read, clone, update, and delete email templates from the CLI

[jbedient-kizen]

Adds get, clone, update, and delete to kizen messages templates, which
could only list before this.

The thing to know before reviewing

An email template stores two independent fields:

• craft_json — the editable node tree the builder UI renders
• content — the compiled, Outlook-safe HTML that is actually sent

The server compiles neither from the other, on POST or on PATCH.
Confirmed live by PATCHing a modified craft_json alone and reading content
back byte-identical. So writing one without the other leaves the builder showing
one email while recipients receive a different one, with nothing anywhere
reporting a problem.

Every design decision in this PR and the ones stacked on it follows from that.

What's here

• get prints the template body plus two drift checks:

  • structure coupled — every Section/Row node has its matching
    section-<nodeId> class in the compiled HTML
  • text in sync — every Text node's copy actually appears there

  --raw dumps the full payload.

• clone always copies both content fields together, making it the safe way
  to branch a design built in the builder UI.

• update/delete PATCH and DELETE directly.

Generating a template from a spec file is deliberately not wired here — that's
the next PR in the stack. The node shapes and compile findings it needs are
written up in kizen docs show email-templates.

Reviewing

9 files, +775/-26. Self-contained: nothing else in the stack is required for
this to be correct on its own.

The drift checks are worth the closest look. They are necessary but not
sufficient — they compare node ids and text, so they cannot see a divergence
where both still match and only styling or width differs. A later PR in the
stack fixes several defects of exactly that shape, all of which these checks
report as green. If you can think of a cheap check that would have caught those,
it's worth adding.