Add optional virtual heat mode with asymmetric hysteresis control

[Claude]

Adds configurable HVAC action monitoring for climate entities with intelligent temperature-based state determination. The Roth Touchline controller doesn't expose heating state, so this implements virtual state tracking based on temperature deltas.

Changes

Config flow:

• Fixed OptionsFlow crash (AttributeError: property 'config_entry' of 'TouchlineOptionsFlow' object has no setter)
• Removed __init__ override—base class manages config_entry via property descriptor
• Changed instantiation from TouchlineOptionsFlow(config_entry) to TouchlineOptionsFlow()
• Added UI option for virtual heat mode toggle

Climate entity:

• Asymmetric hysteresis thresholds:
  • Heating: triggers at ≥0.2°C below target (immediate)
  • Idle: triggers at ≥0.3°C above target (5-minute delay)
  • Hysteresis band: -0.3°C to +0.2°C maintains current state
• State tracking with _is_heating flag and _last_heating_time timestamp
• Returns None when disabled, OFF when HVAC mode is off

Tests:

• Updated threshold values to match asymmetric band
• Fixed floating-point precision issues in exact threshold tests
• All 42 climate + 7 config flow tests passing

Documentation:

• Added Virtual Heat Mode to enhanced features
• Detailed configuration steps and technical behavior
• Example use cases for automations and monitoring

# Hysteresis logic overview
temp_diff = target_temp - current_temp

if temp_diff >= 0.2:  # Below target
    return HVACAction.HEATING
elif temp_diff <= -0.3:  # Above target
    if heating and delay_expired:
        return HVACAction.IDLE
    return current_state
else:  # Within band [-0.3, +0.2]
    return current_state  # Prevent oscillation

[gllmlbrt]

@claude[agent] change the threshold band to - 0.2 / +0.3.

[Claude]

@claude[agent] change the threshold band to - 0.2 / +0.3.

Changed to asymmetric threshold band: -0.2°C for heating / +0.3°C for idle. Heating now triggers when temperature drops 0.2°C below target, while idle triggers when temperature rises 0.3°C above target (after 5min delay). See commit 29309ee.