feat: gateway sub-device discovery (VRF / multi-split support)

[meirlo]

Summary

Adds support for Gree gateway modules that front multiple indoor units (VRF / multi-split systems). A single Wi-Fi gateway exposes several indoor units, each addressed by its own internal MAC inside the encrypted pack while all traffic is routed to the gateway MAC.

With this change, each indoor unit is discovered and surfaced as an ordinary DeviceInfo, so it flows through the existing Discovery -> Device pipeline and can be controlled independently — no API changes are required for existing consumers, and downstream integrations (e.g. Home Assistant) get one device per indoor unit without any integration-side changes.

Closes the "multiple units behind a single Wi-Fi controller" request.

How it works

1. During scan(), a gateway is identified by subCnt > 0 in its discovery response.
2. The library binds to the gateway and sends a subList query, which returns the list of indoor units (each with its own internal MAC).
3. Each indoor unit is emitted as a DeviceInfo carrying the gateway's key/cipher, so it binds by reusing the gateway session (no separate handshake).
4. All status/command messages target the indoor unit by placing its MAC in the pack, while the packet is routed to the gateway MAC.

Changes

Protocol (network.py)

• Add subList command/response and create_sublist_message.
• Add handle_sublist_response; resolve the response type from a top-level t field (subList replies place it outside the pack).
• Make the packet handler registry per-instance. A gateway, its sub-devices and any standalone units coexist as separate DeviceProtocol2 instances; the previous shared class-level dict cross-dispatched callbacks between them and broke bind/state handling once more than one device existed.

Device (device.py)

• Add get_sub_devices() to enumerate a gateway's indoor units via subList.
• bind() auto-inherits the gateway's key and cipher from DeviceInfo.
• target_temperature: tolerate a missing / None / "" TemRec. Sub-devices and command acknowledgements omit the 0.5° rounding bit; default it to 0 instead of dropping the whole setpoint.
• Harden temperature/version parsing against non-numeric values reported by some gateways.

Discovery (discovery.py)

• Parse subCnt; auto-query gateways for their sub-devices during scan().
• Add an include_gateways flag (default False) so the gateway "shell" isn't surfaced as a device.

Device info (deviceinfo.py)

• Add sub_count, plus gateway_key and gateway_cipher (the parent gateway's bound key and live cipher instance) so a sub-device reuses the session.

All new parameters are optional and keyword-only; existing callers are unaffected.

Tests

• subList request/response at the protocol level.
• Per-instance handler isolation (regression test for the shared-dict bug).
• get_sub_devices() success and timeout paths.
• Sub-device binding via explicit key and via gateway-inherited key/cipher.
• Sub-device state updates.
• target_temperature surviving a missing/None TemRec.
• Discovery with subCnt parsing, gateway querying, and the include_gateways flag.

Notes

• Verified end-to-end against real hardware: a 4-unit VRF gateway enumerates and controls each indoor unit independently, alongside a standalone AC on the network.
• Home Assistant needs no code changes to benefit — only a greeclimate version bump in the integration's manifest.json once released.

[meirlo]

this should close Add support for multiple units that connect with a single wifi controller

[codecov]

Codecov Report

❌ Patch coverage is 98.97959% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 96.57%. Comparing base (47b9850) to head (45b6fd5).
⚠️ Report is 22 commits behind head on master.

Files with missing lines	Patch %	Lines
greeclimate/device.py	97.77%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #148      +/-   ##
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+ Coverage   95.71%   96.57%   +0.85%     
==========================================
  Files           8        8              
  Lines         770      846      +76     
==========================================
+ Hits          737      817      +80     
+ Misses         33       29       -4     

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[meirlo]

@cmroche when you have a moment, could you take a look at this PR? 🙏

This adds VRF / multi-split support (multiple indoor units behind a single Wi-Fi gateway), which a lot of people have been waiting for — it comes up regularly in issues and in the Home Assistant community.

A few things that should make review easier:

• Additive and backward-compatible — all new parameters are optional and keyword-only, existing callers are unaffected.
• Library-only — the Home Assistant integration needs no code changes; sub-devices flow through the existing Discovery -> Device pipeline as regular DeviceInfo objects. Once released, HA only needs a greeclimate version bump in its manifest.json.
• Verified on real hardware — a 4-unit VRF gateway enumerates and controls each indoor unit independently, alongside a standalone AC on the same network.
• Cleaned up — rebased on current master, squashed to a single focused commit, with tests covering the protocol, discovery, binding, and state handling.

Happy to make any changes you'd like. Thanks for maintaining this library!

[meirlo]

Closes #101 (which contains the maintainer's own protocol notes for subCnt / subList and links the Home Assistant request home-assistant/core#122200).

Also relevant: #172 addresses mixed-case bindOk responses — this PR resolves the response type case-insensitively in _resolve_response_type, so it handles that casing too.