codex-tools: extract utility tool specs

[bolinfest]

Why

The previous codex-tools migration steps moved the shared schema models, local-host specs, collaboration specs, and related adapters out of codex-core, but core/src/tools/spec.rs still contained a grab bag of pure utility tool builders. Those specs do not need session state or handler logic; they only describe wire shapes for tools that codex-core already knows how to execute.

Moving that remaining low-coupling layer into codex-tools keeps the migration moving in meaningful chunks and trims another large block of passive tool-spec construction out of codex-core without touching the runtime-coupled handlers.

What changed

• extended codex-tools to own the pure spec builders for:
  • code-mode exec / wait
  • js_repl / js_repl_reset
  • MCP resource tools list_mcp_resources, list_mcp_resource_templates, and read_mcp_resource
  • utility tools list_dir and test_sync_tool
• split those builders across small module files with sibling *_tests.rs coverage, keeping src/lib.rs exports-only
• rewired core/src/tools/spec.rs to call the extracted builders and deleted the duplicated core-local implementations
• moved the direct JS REPL grammar seam test out of core/src/tools/spec_tests.rs so it now lives with the extracted implementation in codex-tools
• updated codex-rs/tools/README.md so the documented crate boundary matches the new utility-spec surface

Test plan

• CARGO_TARGET_DIR=/tmp/codex-tools-utility-specs cargo test -p codex-tools
• CARGO_TARGET_DIR=/tmp/codex-core-utility-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
• codex-tools: extract collaboration tool specs #16141