feat(claude-profile): warn when non-Anthropic provider used with OAuth profile

Add a warning when ANTHROPIC_BASE_URL would be set but the active profile's
.credentials.json would override ANTHROPIC_API_KEY with subscription OAuth,
routing requests to Anthropic instead of the intended provider.

Fixes the MiniMax routing issue: use --profile minimax (~/.claude-minimax/,
no stored credentials) for non-Anthropic providers.

Update presets example to use profile: minimax for quick-minimax preset.
63 tests passing.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

data/claude-profile/presets.yaml.example

@@ -40,9 +40,9 @@ hybrid-day:
   time_horizon: hours
   async: yes
 
-# Quick session via MiniMax (Sonnet-class, pay-per-token, no subscription)
+# Quick session via MiniMax — uses the minimax profile (no OAuth credentials)
 quick-minimax:
-  profile: oreillyit
+  profile: minimax
   mode: quick
   provider: minimax-sonnet
   project: small-scripts