v0.94.477

Price sources learn each source's steady premium. Another retailer's
fees no longer pull the blend up or count as forecast error.

• Devhub validation: confirmed live on devhub (HA 2026.10.2) at 21639d0
  (release/0.94.477), installed via HACS and restarted at 14:46; devhub's
  own Nimbus sensors published 0.94.477 by 14:50. The log after the restart
  showed only devhub's known baseline (mirror duplicate-unique-ID notices,
  recorder attribute-size warnings, rename collisions); no price
  consolidation errors. devhub's own plan entity is unavailable (its known
  limitation), so the bias summary is checked on production's first plans.

• Price sources: a steady premium is not forecast error (#1786). A source
  priced on another contract (e.g. a retailer that adds hedging and fees per
  kWh) sits a steady amount above the provider's settled price. Each source's
  signed error is now tracked per lead as a bias; its MAE scores what is left
  after removing it, and once a source has earned a weight it joins the blend
  with its bias removed, so the blend is no longer pulled up by another
  contract's fees. The table still shows each source's own price, spikes are
  still judged on raw prices, and the spread is unchanged. Shadow only while
  consolidation is off.