Fix SignalsAPI.stake_get (KeyError on removed totalStake field)

[lingster]

Problem

SignalsAPI.stake_get raised KeyError: 'totalStake' on every call:

data = self.public_user_profile(username)
return data['totalStake']

totalStake was once part of the profile query but was dropped when the query
was migrated to v2SignalsProfile and then v3UserProfile. The field no
longer exists on the V3UserProfile type at all, so the lookup always failed.

Fix

Query the current stake field, stakeValue (type Nmr), directly within the
signals tournament and parse it to Decimal, returning None for models with
no stake (instead of raising):

query = '''
  query($model_name: String!, $tournament: Int) {
    v3UserProfile(model_name: $model_name, tournament: $tournament) {
      stakeValue
    }
  }
'''

Testing (red/green TDD)

• New test_stake_get (asserts stakeValue is queried, totalStake is not,
  and the request is scoped to tournament 11) and test_stake_get_no_stake
  (null stake → None). Written failing first.
• Full suite: 44 passed (live-API tests deselected); pyflakes clean.
• Live check: SignalsAPI().stake_get("uuazed") now returns a real
  Decimal instead of raising; an unstaked model returns None.

🤖 Generated with Claude Code