Add saved starter words for signed-in players

Players can save up to 3 favorite opening words and tap one to fill the
current row. Words are stored on profiles.starter_words and saved through
the set_starter_words RPC, which validates them against the dictionary.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

supabase/schema.sql

@@ -18,7 +18,15 @@ create table if not exists public.profiles (
 );
 
 alter table public.profiles
-  add column if not exists username text;
+  add column if not exists username text,
+  add column if not exists starter_words text[] not null default '{}';
+
+alter table public.profiles
+  drop constraint if exists profiles_starter_words_limit;
+
+alter table public.profiles
+  add constraint profiles_starter_words_limit
+  check (cardinality(starter_words) <= 3);
 
 create unique index if not exists profiles_username_key
   on public.profiles (lower(username))
@@ -490,6 +498,50 @@ begin
 end;
 $$;
 
+create or replace function public.set_starter_words(words text[])
+returns text[]
+language plpgsql
+security definer
+set search_path = public
+as $$
+declare
+  normalized_words text[];
+begin
+  if auth.uid() is null then
+    raise exception 'Sign in to save starter words';
+  end if;
+
+  select coalesce(array_agg(word order by first_position), '{}')
+    into normalized_words
+  from (
+    select lower(trim(candidate)) as word, min(position) as first_position
+    from unnest(coalesce(words, '{}')) with ordinality as input(candidate, position)
+    where nullif(trim(candidate), '') is not null
+    group by lower(trim(candidate))
+  ) deduped;
+
+  if cardinality(normalized_words) > 3 then
+    raise exception 'You can save up to 3 starter words';
+  end if;
+
+  if exists (
+    select 1
+    from unnest(normalized_words) as candidate(word)
+    where candidate.word !~ '^[a-z]{5}$'
+      or not exists (select 1 from public.wordle_dictionary dictionary where dictionary.word = candidate.word)
+  ) then
+    raise exception 'Not in word list';
+  end if;
+
+  update public.profiles
+  set starter_words = normalized_words,
+      updated_at = now()
+  where id = auth.uid();
+
+  return normalized_words;
+end;
+$$;
+
 create or replace function public.get_player_current_streak(target_user_id uuid)
 returns integer
 language plpgsql
@@ -743,6 +795,7 @@ grant select, update on public.profiles to authenticated;
 grant select on public.wordle_rounds to authenticated;
 grant select on public.wordle_guesses to authenticated;
 grant execute on function public.is_username_available(text) to anon, authenticated;
+grant execute on function public.set_starter_words(text[]) to authenticated;
 grant execute on function public.require_confirmed_email() to authenticated;
 grant execute on function public.start_hourly_round() to authenticated;
 grant execute on function public.submit_guess(uuid, text) to authenticated;