fix(anthropic): add Claude Opus 4.8 support (adaptive thinking + pricing)

[GrantablePD]

Problem

Production Hermes (Slack) is failing on every turn with HTTP 400:

"thinking.type.enabled" is not supported for this model. Use "thinking.type.adaptive" and "output_config.effort" to control thinking behavior.

Root cause

agent/anthropic_adapter.py gates adaptive-thinking behavior on hardcoded version substrings that only knew about Claude 4.6 and 4.7. With Opus 4.8 now in use, _supports_adaptive_thinking() returned False, so the adapter fell to the manual-thinking else branch and sent the legacy thinking: {type: "enabled", budget_tokens: …} payload — which 4.8 rejects.

Fix

Teach the adapter about 4.8 (mirrors upstream NousResearch#34003):

• _ADAPTIVE_THINKING_SUBSTRINGS, _XHIGH_EFFORT_SUBSTRINGS, _NO_SAMPLING_PARAMS_SUBSTRINGS now include "4-8"/"4.8"
• output-limit (128k) + 1M context-window entries for claude-opus-4-8
• usage pricing for claude-opus-4-8 and the -fast variant
• claude-opus-4.8 + claude-opus-4.8-fast added to the model pickers

Fast mode is intentionally left unchanged — Opus 4.8's fast offering is a separate model id (claude-opus-4.8-fast), not the speed=fast parameter.

Conflicts

Cherry-picked from upstream 1a7479573. The adapter + model-metadata + test hunks applied cleanly; conflicts in the fork-curated models.py / usage_pricing.py / model-catalog.json were resolved to preserve our curation while adding the 4.8 entries.

Verification

• tests/agent/test_anthropic_adapter.py + test_model_metadata.py: 230 passed. The only 11 failures are pre-existing/environmental (credential-resolution tests that read real ANTHROPIC_* env vars + ~/.claude creds present on the dev machine) — unrelated to this change.
• Thinking/effort/4.8 test classes: 33 passed.
• Direct behavioral check confirms claude-opus-4-8 (all id forms) → adaptive=True, xhigh=True, no_sampling=True, max_out=128000, and no regression (4.6 still adaptive, 4.5 still manual).

Deploy note

The fix takes effect once the Railway hermes-agent service redeploys from this branch's merge to main.

🤖 Generated with Claude Code