codex-tools: extract collaboration tool specs

[bolinfest]

Why

The recent codex-tools migration steps have moved shared tool models and low-coupling spec helpers out of codex-core, but core/src/tools/spec.rs still owned a large block of pure collaboration-tool spec construction. Those builders do not need session state or runtime behavior; they only need a small amount of core-owned configuration injected at the seam.

Moving that cohesive slice into codex-tools makes the crate boundary more honest and removes a substantial amount of passive tool-spec logic from codex-core without trying to move the runtime-coupled multi-agent handlers at the same time.

What changed

• added agent_tool.rs, request_user_input_tool.rs, and agent_job_tool.rs to codex-tools, with sibling *_tests.rs coverage and an exports-only lib.rs
• moved the pure ToolSpec builders for:
  • collaboration tools such as spawn_agent, send_input, send_message, assign_task, resume_agent, wait_agent, list_agents, and close_agent
  • request_user_input
  • agent-job specs spawn_agents_on_csv and report_agent_job_result
• rewired core/src/tools/spec.rs to call the extracted builders while still supplying the core-owned inputs, such as spawn-agent role descriptions and wait timeout bounds
• updated the core/src/tools/spec.rs seam tests to build expected collaboration specs through codex-tools
• updated codex-rs/tools/README.md so the crate documentation reflects the broader collaboration-tool boundary

Test plan

• CARGO_TARGET_DIR=/tmp/codex-tools-collab-specs cargo test -p codex-tools
• CARGO_TARGET_DIR=/tmp/codex-core-collab-specs cargo test -p codex-core --lib tools::spec::
• just fix -p codex-tools -p codex-core
• just argument-comment-lint

References

• codex-tools: extract shared tool schema parsing #15923
• codex-tools: extract MCP schema adapters #15928
• codex-tools: extract dynamic tool adapters #15944
• codex-tools: introduce named tool definitions #15953
• codex-tools: extract responses API tool models #16031
• codex-tools: extract tool spec models #16047
• codex-tools: extract configured tool specs #16129
• codex-tools: extract code mode tool spec adapters #16132
• codex-tools: extract local host tool specs #16138