Add YAML metadata support for genericmiot

[Acrobot]

Implements the metadata approach from #1618, adapted to the current codebase where descriptor creation has moved into the miot models.

Adds a YAML-based metadata system that enriches genericmiot descriptors with human-readable descriptions, replacing the vendor-provided, often-Chinese defaults from miotspec files:

• Metadata is organized into namespace YAML files mirroring the MIoT URN namespace structure
• A fallback chain allows dreame-specific services to fall back to miot-spec-v2, and all namespaces (including unknown ones) to fall back to common
• A __ANY__ wildcard service in common provides cross-service property descriptions (temperature, humidity, CO2, PM2.5/PM10, voltage, etc.) without per-service repetition
• Descriptor enrichment is non-mutating: the original descriptor is preserved in extras['original'] for callers that need the raw device-given name

Design

• meta.py: Metadata class loads YAML namespace files and looks up metadata by URN namespace, service, type, and entity name
• metadata/base.yaml: index mapping namespace names to YAML files
• metadata/miotspec.yaml: definitions for miot-spec-v2 (battery, vacuum, filter, brush, light, identify services)
• metadata/dreamespec.yaml: definitions for dreame-spec (vacuum-extend, DnD, audio, clean-logs, time services); falls back to miot-spec-v2
• metadata/common.yaml: cross-namespace definitions under a __ANY__ wildcard service (MAC address, voltage, temperature, humidity, CO2, PM2.5/PM10, brightness, cleaning stats); implicit fallback for all namespaces including unknown ones
• genericmiot.py: _enrich_with_metadata() returns a new descriptor via attr.evolve with the metadata name; the original descriptor is preserved in extras['original'] for callers that need the raw device-given name

Namespace fallback chain

dreame-spec → miot-spec-v2 → common
<any unknown namespace> → common

Namespaces declare their fallback with a fallback: key. common is the implicit fallback for all namespaces. Within each namespace, the __ANY__ wildcard service matches properties regardless of which service they belong to.

Model-specific namespaces (keyed by urn.model) are a natural future extension: add a model YAML file with a fallback: pointing to the relevant namespace.

[Acrobot]

These changes were generated using Claude Code under my supervision. I reviewed and approved all code before submitting. I'm not very familiar with this codebase, so apologies in advance for any mistakes.

[codecov]

Codecov Report

❌ Patch coverage is 97.32143% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 84.27%. Comparing base (2817647) to head (01c3805).

Files with missing lines	Patch %	Lines
miio/integrations/genericmiot/meta.py	95.71%	2 Missing and 1 partial ⚠️
miio/integrations/genericmiot/genericmiot.py	85.71%	2 Missing ⚠️
miio/miot_models.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2062      +/-   ##
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+ Coverage   84.13%   84.27%   +0.14%     
==========================================
  Files         199      201       +2     
  Lines       20164    20386     +222     
  Branches     1063     1073      +10     
==========================================
+ Hits        16964    17181     +217     
- Misses       3010     3014       +4     
- Partials      190      191       +1     

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[rytilahti]

Thanks a lot for this PR, @Acrobot! Now that I have a real device to test against, I did some rewiring based on how I felt it should behave.

I did quite a few cleanups to keep it simple (and not bound to homeassistant specifics like device_classes and icons), but this might be extended later. I am planning to do some more improvements to stress test the design & to add proper support for my airmonitor (urn:miot-spec-v2:device:air-monitor:0000A008:cgllc-cgd1st:1), but I will save the improvements into separate PRs.