fix(anthropic): live model fetching + adaptive thinking for 4.5+ models

- Add _fetch_anthropic_models() to hermes_cli/models.py — hits the
  Anthropic /v1/models endpoint to get the live model catalog. Handles
  both API key and OAuth token auth headers.

- Wire it into provider_model_ids() so both 'hermes model' and
  'hermes setup model' show the live list instead of a stale static one.

- Update static _PROVIDER_MODELS fallback with full current catalog:
  opus-4-6, sonnet-4-6, opus-4-5, sonnet-4-5, opus-4, sonnet-4, haiku-4-5

- Update model_metadata.py with context lengths for all current models.

- Fix thinking parameter for 4.5+ models: use type='adaptive' instead
  of type='enabled' (Anthropic deprecated 'enabled' for newer models,
  warns at runtime). Detects model version from the model name string.

Verified live:
  hermes model → Anthropic → auto-detected creds → shows 7 live models
  hermes chat --provider anthropic --model claude-opus-4-6 → works

agent/model_metadata.py

@@ -42,6 +42,11 @@ DEFAULT_CONTEXT_LENGTHS = {
     "anthropic/claude-sonnet-4-20250514": 200000,
     "anthropic/claude-haiku-4.5": 200000,
     # Bare Anthropic model IDs (for native API provider)
+    "claude-opus-4-6": 200000,
+    "claude-sonnet-4-6": 200000,
+    "claude-opus-4-5-20251101": 200000,
+    "claude-sonnet-4-5-20250929": 200000,
+    "claude-opus-4-1-20250805": 200000,
     "claude-opus-4-20250514": 200000,
     "claude-sonnet-4-20250514": 200000,
     "claude-haiku-4-5-20251001": 200000,