arch(protocol): move remaining OpenWebNet string/dimension edge-case decoding to OWNd and remove production shims/MagicMock checks #736

Architectural Assessment & Severity

• Critique Point: Heating - WHO4 - Error list index out of range #7 — Protocol edge-case accumulation instead of stricter modeling
• Severity: P1 (High — Rank Installing this integration in an HA instance running on Docker #5)
• Related Issues: OWNd#60, OWNd#97, OWNd#102, Spurious ERROR logged on startup discovery when subsystems are not present (*#4*0##, *#16*0##) #406

Problem Statement

While custom_components/myhome/where_grammar.py (enforced by tests/test_where_usage_guard.py) successfully centralized WHO=4 WHERE grammar (1..99 zone, #0 central unit, Z#N actuator, 0#N pump, PZZ probe), several other OpenWebNet protocol edge cases and string-parsing workarounds have accumulated inside MyHOME instead of being strictly modeled in OWNd:

1. WHO=1 APL / Area-0 Addressing & Timer Frame String Construction in const.py:
   • is_apl_address(), area_of_where(), and normalize_where() (custom_components/myhome/const.py:244-321) implement OpenWebNet 2-digit vs. 4-digit APL and Area 00 / 100 string parsing directly in Home Assistant.
   • build_timed_turn_on_command() (const.py:519-555) formats raw *1*{what}*{where}## and *#1*{where}*#2*{h}*{m}*{s}## frame strings as fallbacks.
2. WHO=1 Group Dimension Private-Attribute Parsing in light_group.py:
   • MyHOMELightGroup.handle_event() (custom_components/myhome/light_group.py:180-196) reaches into getattr(msg, "_dimension_value", []) and manually decodes Dimension 1 (raw - 100 for 100 <= raw <= 200), Dimension 14 (int(1000000 / int(vals[0]))), and Dimension 12 (h <= 360 sentinel check for *12*511*127*255), duplicating OWNLightingEvent parsing.
3. WHO=4 Sign-Magnitude Temperature Decoding in const.py:
   • who4_raw_to_celsius() (custom_components/myhome/const.py:214-222) decodes 4-digit SXXX temperature strings (1xxx negative, 0xxx positive tenths of °C) in MyHOME when OWNd leaves raw dimension values undecoded.
4. WHO=16 Stepped Volume (WHAT=1001..1015 / 1101..1115) String Splitting in media_player_power.py:
   • apply_volume_delta_from_what() (custom_components/myhome/media_player_power.py:57-92) splits what.split("#", 1)[0] and checks 1001 <= what_code <= 1015 / 1101 <= what_code <= 1115 to compute step / 31.0 because OWNSoundDiffusionEvent (OWNd/message/sound.py) only maps discrete WHAT codes in _SOUND_WHAT_TABLE.
5. Obsolete OWNd Shims & MagicMock Checks in Production Code:
   • try ... except ImportError shims in climate.py:49-55 (MESSAGE_TYPE_SEASON, merged in OWNd#97) and sensor.py:39-48 (MESSAGE_TYPE_AUTO_UPDATE_INTERVAL, merged in OWNd#102), plus MESSAGE_TYPE_ZONE_STATE = "zone_state" in climate.py:90 (OWNd#60).
   • _StatusRequestLogFilter in gateway.py:128-146 mutating OWNd log records in-place for OWNd < 2.0.0b8.
   • 5 production checks for MagicMock (gateway_events.py:285, 327, gateway_resync.py:124, sensor.py:849, services.py:77).

Proposed Solution (PR Scope)

1. Extend Typed Protocol Models in OWNd:
   • Export MESSAGE_TYPE_ZONE_STATE (WHO=4 Dimension 7) and ensure all WHO=4 temperature dimensions decode sign-magnitude SXXX values in OWNHeatingEvent.
   • Decode WHO=16 stepped volume WHAT=1001..1015 (+1..+15) and WHAT=1101..1115 (-1..-15) as a typed volume_step_delta: int | None property on OWNSoundDiffusionEvent.
   • Expose typed brightness, color_temp_kelvin, and hs_color properties on WHO=1 group dimension commands/events (*#1*#G*#D*...##) in OWNd/message/lighting.py.
   • Move is_apl_address, area_of_where, and normalize_where into OWNd's addressing module (and re-export in MyHOME alongside where_grammar.py).
2. Purge Protocol Hacks, Shims & MagicMock Checks in MyHOME:
   • Replace raw _dimension_value parsing in light_group.py, what.split("#") volume math in media_player_power.py, and who4_raw_to_celsius in const.py with typed OWNd properties.
   • Delete the obsolete ImportError shims in climate.py and sensor.py and _StatusRequestLogFilter in gateway.py.
   • Remove all 5 MagicMock checks from custom_components/myhome/ and fix test mocks to supply typed attributes.
   • Add an AST/regex guard test in tests/test_where_usage_guard.py forbidding MagicMock references and private _dimension_value accesses inside custom_components/myhome/.

Verification Plan

• Run pytest tests/test_where_usage_guard.py (extended with protocol boundary and no-MagicMock guards).
• Run full test suite against the updated OWNd package (pytest tests -q --cov=custom_components/myhome) and ruff check.