Conflicts resolved in agent_models.rs / agent_models_tests.rs: main's #2890
(live Databricks discovery via effective_discovery_provider +
provider_env_var) composed with this branch's unified
resolve_effective_harness_descriptor. get_agent_models now passes the
record's saved provider plus the runtime's provider_env_var (from
known_acp_runtime on the descriptor command) into
effective_discovery_provider, replacing both main's
SavedAgentModelDiscoveryConfig snapshot and this branch's ad-hoc
BUZZ_AGENT_PROVIDER env read.
Co-authored-by: Tyler Longwell <tlongwell@block.xyz>
Signed-off-by: Tyler Longwell <tlongwell@block.xyz>