chore(models): move the opus alias to claude-opus-5

Claude Opus 5 released today — same $5/$25 sticker, 1M context; Opus 4.8
moves to legacy. The pricing table gains a dedicated claude-opus-5
fragment (the claude-opus-4 substring doesn't cover it, so without the
row the fleet's Opus usage would silently cost-track as $0 — exactly
what test_opus_is_priced now guards).

tests/unit/services/test_audit_agent_id.py

@@ -182,7 +182,7 @@ async def test_log_agent_event_resolves_slug_to_uuid(
         event_type="agent.spawned",
         agent_slug=slug,
         task_id=task_id,
-        details={"container_id": "abc123def456", "model": "claude-opus-4-8"},
+        details={"container_id": "abc123def456", "model": "claude-opus-5"},
     )
 
     # Read back the row.

tests/unit/services/test_usage.py

@@ -945,7 +945,7 @@ class TestGetRecentSessions:
         row = MagicMock()
         row.id = sid
         row.agent_slug = "product-owner"
-        row.model = "claude-opus-4-8"
+        row.model = "claude-opus-5"
         row.started_at = datetime.datetime(2026, 6, 11, 20, 41, tzinfo=datetime.UTC)
         row.ended_at = datetime.datetime(2026, 6, 11, 20, 42, tzinfo=datetime.UTC)
         row.tokens_input = exp_in
@@ -966,7 +966,7 @@ class TestGetRecentSessions:
         s = out[0]
         assert s["id"] == str(sid)
         assert s["agent_slug"] == "product-owner"
-        assert s["model"] == "claude-opus-4-8"
+        assert s["model"] == "claude-opus-5"
         assert s["tokens_input"] == exp_in
         assert s["tokens_output"] == exp_out
         assert s["tokens_cache"] == exp_cr + exp_cw