## Summary
Multi-agent v2 tools now use the fixed `collaboration` namespace when
namespace tools are available. This keeps the model-visible hint and the
actual tool surface aligned around `functions.collaboration.*`, without
exposing an unshipped namespace knob to users.
The PR also removes the old `features.multi_agent_v2.tool_namespace`
config/schema surface, updates the MAv2 test fixtures for namespaced
calls, and fixes stale `TurnContext.features` references that were
breaking `codex-core` builds.
## Changes
- Expose MAv2 tools under `collaboration` instead of relying on a
configurable namespace.
- Remove `tool_namespace` from MAv2 TOML config, resolved config,
validation, schema, and tests.
- Update tool-planning and integration fixtures to assert or emit
namespaced MAv2 tool calls.
- Read feature state through `TurnContext.config.features` in the
multi-agent mode context paths.
## Testing
- `just write-config-schema`
- `just test -p codex-features`
jif
49614a0391