rename: unit/sub-unit -> subdevice, matching OCF terminology

"Unit"/"sub-unit" from #199's multi-indoor-device support wasn't OCF
idiomatic -- OCF calls each component of a composite device a
"subdevice" (see subdeviceIdList), so rename SubUnit -> Subdevice
throughout: the registry module, coordinator state, BoundEntity's
subdevice field, diagnostics keys (subdevices/subdevices_skipped/
subdevice_probes), entity unique_id prefixes (unit1_/sub_<uuid>_ ->
subdevice1_/subdevice_<uuid>_), device-name fallback labels, golden
fixtures, tests, README, and the adding-device-support skill.

Breaking change to entity unique_ids and diagnostics keys, acceptable
since this hasn't been released yet.

tests/test_coordinator_send_command.py

@@ -28,7 +28,7 @@ from custom_components.localthings.registry.capabilities import laundry
 from custom_components.localthings.registry.capabilities.airconditioner import _climate_write
 from custom_components.localthings.registry.discovery import BoundEntity
 from custom_components.localthings.registry.entities import ClimateDesc
-from custom_components.localthings.registry.subunits import SubUnit
+from custom_components.localthings.registry.subdevices import Subdevice
 
 ENTRY_DATA = {
     CONF_HOST: '10.0.0.199',
@@ -98,26 +98,26 @@ async def test_options_write_optimistic_cache_keeps_sibling_tokens(coordinator)
 
 
 # ---------------------------------------------------------------------------
-# Sub-unit write translation (issue #177): a composite-entity write_fn (here
+# Subdevice write translation (issue #177): a composite-entity write_fn (here
 # airconditioner._climate_write) returns *canonical* path_segs
 # (['power', 'vs', '0']) -- async_send_command must translate that through
-# bound_entity.sub_unit.to_actual before POSTing, applying the optimistic
-# value, and starting the settle guard, or a sub-unit's climate card would
+# bound_entity.subdevice.to_actual before POSTing, applying the optimistic
+# value, and starting the settle guard, or a subdevice's climate card would
 # write to (and read confirmation from) the master's resource instead of
 # its own.
 # ---------------------------------------------------------------------------
 
-def _climate_bound(href: str, sub_unit: SubUnit) -> BoundEntity:
+def _climate_bound(href: str, subdevice: Subdevice) -> BoundEntity:
     desc = ClimateDesc(key='climate', translation_key='airconditioner',
                         write_fn=_climate_write)
-    return BoundEntity(href=href, capability=None, desc=desc, sub_unit=sub_unit)
+    return BoundEntity(href=href, capability=None, desc=desc, subdevice=subdevice)
 
 
-async def test_indexed_sub_unit_write_posts_to_translated_path(coordinator) -> None:
-    """A power write from the bedroom unit's (indexed '1') climate entity
+async def test_indexed_subdevice_write_posts_to_translated_path(coordinator) -> None:
+    """A power write from the bedroom subdevice's (indexed '1') climate entity
     must POST to /power/vs/1, not the master's /power/vs/0."""
-    unit1 = SubUnit(kind='indexed', key='1', seed_path=('device', '1'))
-    bound = _climate_bound('/mode/vs/1', unit1)
+    sub1 = Subdevice(kind='indexed', key='1', seed_path=('device', '1'))
+    bound = _climate_bound('/mode/vs/1', sub1)
 
     await coordinator.async_send_command(bound, ('power', True))
 
@@ -126,11 +126,11 @@ async def test_indexed_sub_unit_write_posts_to_translated_path(coordinator) -> N
     assert cbor2.loads(posted_bytes) == {'x.com.samsung.da.power': 'On'}
 
 
-async def test_indexed_sub_unit_write_applies_optimistic_value_to_translated_href(
+async def test_indexed_subdevice_write_applies_optimistic_value_to_translated_href(
     coordinator,
 ) -> None:
-    unit1 = SubUnit(kind='indexed', key='1', seed_path=('device', '1'))
-    bound = _climate_bound('/mode/vs/1', unit1)
+    sub1 = Subdevice(kind='indexed', key='1', seed_path=('device', '1'))
+    bound = _climate_bound('/mode/vs/1', sub1)
 
     await coordinator.async_send_command(bound, ('power', True))
 
@@ -142,7 +142,7 @@ async def test_indexed_sub_unit_write_applies_optimistic_value_to_translated_hre
     # The settle guard is armed on that same translated href: a stale poll
     # reporting the pre-write value must be dropped, not allowed to revert
     # the optimistic 'On' (issue #27's regression, translated to a
-    # sub-unit's own resource).
+    # subdevice's own resource).
     applied = coordinator._observe.apply(
         '/power/vs/1', {'x.com.samsung.da.power': 'Off'}, source='poll',
     )
@@ -150,12 +150,12 @@ async def test_indexed_sub_unit_write_applies_optimistic_value_to_translated_hre
     assert coordinator._cache.get('/power/vs/1') == {'x.com.samsung.da.power': 'On'}
 
 
-async def test_prefixed_sub_unit_write_posts_to_translated_path(coordinator) -> None:
-    """A power write from a UUID-prefixed unit's climate entity must POST
+async def test_prefixed_subdevice_write_posts_to_translated_path(coordinator) -> None:
+    """A power write from a UUID-prefixed subdevice's climate entity must POST
     to /<uuid>/power/vs/0, not the bare canonical href."""
     sub_id = '6c2dff6d-ee5c-dad1-6a5e-000000000001'
-    unit = SubUnit(kind='prefixed', key=sub_id, seed_path=(sub_id, 'device', '0'))
-    bound = _climate_bound(f'/{sub_id}/mode/vs/0', unit)
+    subdevice = Subdevice(kind='prefixed', key=sub_id, seed_path=(sub_id, 'device', '0'))
+    bound = _climate_bound(f'/{sub_id}/mode/vs/0', subdevice)
 
     await coordinator.async_send_command(bound, ('power', True))
 
@@ -167,11 +167,11 @@ async def test_prefixed_sub_unit_write_posts_to_translated_path(coordinator) ->
     }
 
 
-async def test_main_climate_write_unaffected_by_sub_unit_translation(coordinator) -> None:
+async def test_main_climate_write_unaffected_by_subdevice_translation(coordinator) -> None:
     """MAIN's to_actual is the identity transform -- a device with no
-    sub-units must keep posting to the exact same path as before this
+    subdevices must keep posting to the exact same path as before this
     translation step existed."""
-    from custom_components.localthings.registry.subunits import MAIN
+    from custom_components.localthings.registry.subdevices import MAIN
     bound = _climate_bound('/mode/vs/0', MAIN)
 
     await coordinator.async_send_command(bound, ('power', True))