Dispatch DELETE in do_request

[tomchop]

do_request dispatched GET, POST and PATCH and raised ValueError: Unsupported method: DELETE for anything else. That is the reason the 2.3.0 notes had to say "No delete_agent_persona: do_request dispatches GET, POST and PATCH only", and the reason there is no delete_dfiq either.

The practical effect is worse than a missing method: anyone needing to delete has to reach past the wrapper into self.client, which skips the 401 refresh-and-retry and the YetiApiError wrapping that every other call gets. I hit this cleaning up after a live test of #27.

Scope

Two lines of dispatch. No delete_* convenience methods — this only removes what was blocking them. Adding delete_dfiq, delete_agent_persona and friends is a separate question about which deletions the client should expose.

Verification

Unit and type checks, run the way CI does via poetry install --no-root:

• poetry run python -m unittest tests/api.py — 39 passed (2 new: DELETE dispatches to Session.delete, and an unknown method still raises)
• poetry run pyrefly check — 0 errors

Also driven against a live Yeti, creating a DFIQ scenario and deleting it through the wrapper:

created: 17361959
do_request("DELETE") returned: b'null'
still there? False

Release

Version bumped to 2.4.0 — additive behaviour on a public method, so a minor. As with 2.3.1 the bump rides in here so no second commit has to land on protected main; the tag and published release are still a separate step, and there is no urgency to cut one.