Simplify table-scoped translation key; fix stale resolution; correct docstring

Simplification (feedback: this was overcomplicated): drop the
validated_table gate entirely. cycle_select's table_href now just builds
the translation key directly from whatever course table the device
reports (washer_cycle + Table_02 -> washer_cycle_table_02) instead of
comparing against a hardcoded known-good value and falling back to no key
on any mismatch. A table we haven't shipped translations for yet (e.g.
FlexWash's Table_00) still gets a key built for it -- Home Assistant's own
missing-translation handling takes it from there, the same graceful
fallback already relied on for any individual untranslated code within an
existing table. Adding a newly-confirmed table later is just new
strings.json entries, no code change.

Independent (Opus) review of the prior version caught two real issues,
fixed here regardless of the simplification above:

- translation_key was resolved once at entity construction from whatever
  coordinator.last_resources held at that moment. Discovery can run while
  a sibling resource is still an empty stub (documented precedent: see
  _is_included), so a callable translation_key could permanently bake in
  a stale value for the entity's lifetime. Moved resolution into a
  translation_key property override (Entity.translation_key is a property
  upstream, not a plain attribute), re-evaluated against live coordinator
  data on every access, matching how options/current_option already work.

- The supportedOptions fallback's "smallest passing K wins" docstring
  claimed every larger passing K is an exact multiple of the true one.
  False: the shipped dishwasher fixture has passing K=7 (true) alongside
  10, 14, and 35, none of which are multiples of 7 -- position 0 always
  lands on the same real course code regardless of K, which alone
  satisfies the current-course guard for several unrelated splits.
  Corrected the reasoning to what's actually true (an empirically-matched
  heuristic across six real dumps, not a proof) and added a regression
  test locking in the real dishwasher case so this isn't silently lost.

tests/test_select_options.py

@@ -57,3 +57,20 @@ def test_callable_options_empty_result():
     desc = SelectDesc(key='cycle', options=lambda resources: [])
     entity = _make_select(desc, '/x/vs/0', {})
     assert entity.options == []
+
+
+def test_callable_translation_key_reresolves_live_not_once_at_construction():
+    """A callable translation_key (laundry.cycle_select's table-id-gated
+    resolver) must be re-evaluated against current coordinator data on
+    every access, not baked in once at __init__ -- discovery can run while
+    a sibling resource (e.g. /st/washercourse/vs/0) is still an empty stub
+    (see entity.py's _is_included docstring), and a one-time resolution
+    would permanently show untranslated codes even after a later poll
+    populates the real value."""
+    desc = SelectDesc(key='cycle', translation_key=lambda resources: resources.get('key'))
+    resources = {'key': None}
+    entity = _make_select(desc, '/x/vs/0', resources)
+    assert entity.translation_key is None
+
+    resources['key'] = 'washer_cycle_table_02'
+    assert entity.translation_key == 'washer_cycle_table_02'