Make multi-agent v2 tool namespace configurable

[jif-oai]

Summary

• Add features.multi_agent_v2.tool_namespace with config/schema validation for Responses-compatible namespace values.
• Thread the resolved namespace into ToolsConfig for normal turns and review turns.
• Wrap MultiAgentV2 tool specs and registry names in the configured namespace when namespace tools are supported, while falling back to the plain tool names when they are not.

Validation

• just fmt
• just write-config-schema
• cargo test -p codex-features multi_agent_v2_feature_config -- --nocapture
• cargo test -p codex-core test_build_specs_multi_agent_v2 -- --nocapture
• cargo test -p codex-core multi_agent_v2_config -- --nocapture
• cargo test -p codex-core multi_agent_v2_rejects_invalid_tool_namespace -- --nocapture
• cargo test -p codex-tools
• git diff --check

[jif-oai]

@codex review

[chatgpt-codex-connector]

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[jif-oai]

@codex review

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 77ae0fa4ec

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".