Fix IntesisBox local (WMP) path: CR terminator, tolerant init, ack returns, keepalive and reconnect

[i6media]

Fixes #86.

This makes the IntesisBox (WMP local protocol) path work end-to-end. All five issues from #86 are addressed, each verified against real hardware: an INWMPMHI001R000 (MH-RC-WMP-1, WMP firmware v1.3.3) on a Mitsubishi Heavy FDUM71VH ducted unit, driven through hass-intesishome. With this branch the device connects, initialises, polls, accepts commands and survives socket loss.

Changes

1. CR terminator — IntesisBox now overrides _send_command to guarantee the \r the WMP protocol requires. Previously only SET carried one, so ID/LIMITS/GET were never parsed by the device and connecting always ended in cannot_connect.
2. Tolerant init — the LIMITS:* discovery queries are sent with wait_for_response=False. A unit without a feature never answers that feature's LIMITS query (the ducted unit is completely silent on LIMITS:VANELR, no ERR), which used to trip the 5s timeout and close the socket mid-init.
3. Ack returns — IntesisBase._send_command now returns a bool (written + response frame arrived in time), and the IntesisBox set_* methods return it, matching the cloud classes' documented contract. They returned None, which consumers like hass-intesishome treat as an unacknowledged command — every service call raised after the ONOFF byte had already gone out, aborting the mode/setpoint steps that follow. set_mode also returns False for a mode the map doesn't know instead of silently doing nothing.
4. Keepalive actually runs — connect() now schedules the existing _send_keepalive loop, which was never created anywhere. Besides keeping the otherwise idle socket alive, its blocking wait doubles as a dead-socket detector (a missed reply closes the writer within ~35s instead of "whenever the user next sends a command").
5. Reconnect — IntesisBox implements the _handle_disconnect hook with a capped exponential backoff loop (15s → 300s), guarded by a stopped flag so an intentional stop() stays stopped.

Tests

Adds IntesisBox coverage via a fake WMP TCP device (FakeWMPServer in tests/__init__.py, replacing the NotImplementedError placeholder callback), mirroring the real device's behaviour including the silent LIMITS:VANELR. New tests cover: init with an unanswered LIMITS query, the CR-terminated command stream, keepalive task creation, bool returns for acknowledged / unanswered / invalid commands, reconnect after connection loss, and stop() suppressing the reconnect loop.

pytest (94 passed) and pylint (10.00/10) both clean.

[jnimmo]

Thanks very much @i6media