2026.09.03

Add ministral-14b-latest (Ministral 3 14B, released Dec 2025): the
new, largest model in the Ministral 3 edge family, positioned above
8B/3B and below Small in the dropdown.

• Remove open-mistral-nemo (Mistral Nemo 12B): deprecated and retired
  per Mistral's own model lifecycle table, no longer callable.
• Remove the dead pinned mistral-medium-2505 entry from
  AGENT_CAPABLE_MODELS ('-latest' aliases already track current
  versions automatically; a pinned deprecated ID served no purpose).
• Add translation_key="model" to the model SelectSelector in
  config_flow.py so per-option notes can be shown in the options
  dialog dropdown (strings.json / translations use
  selector.model.options for this).
• Add a per-model free-tier note to the config dialog (EN/NL/FR):
  Ministral 3B/8B/14B and Mistral Small are marked free-tier friendly;
  Mistral Medium and Mistral Large are flagged as paid-tier models
  that are often rate-limited or rejected on free/Experiment API keys.
  Mistral does not publish an official per-model block list for the
  free tier, so this is worded as an observed pattern rather than a
  documented guarantee.
• Update README's model table to match: add ministral-14b-latest and
  mistral-medium-latest rows, drop open-mistral-nemo, add a 'Free
  tier' column with the same caveat as the dialog note.