[wip]tool-api: move extension-facing tool bundles out of codex-tools

[jif-oai]

Why

codex-tool-api and codex-tools still have different jobs.

codex-tool-api is the small authoring surface that a tool-owning extension crate should depend on. It needs enough to describe and execute an ordinary contributed function tool: ToolBundle, ToolExecutor, ToolCall, ToolError, ToolName, JsonSchema, and namespace metadata.

codex-tools remains host-side. It owns the Responses API wire types and the logic that aggregates built-in tools, MCP tools, dynamic tools, and extension bundles into the model-visible/runtime tool surface. That includes namespace rendering, code-mode augmentation, MCP/dynamic conversion, discovery, and other host-only shaping.

Keeping both crates lets us prove the reusable external tool seam without dragging host-only machinery back into extension crates.

What changed

• move the extension-facing bundle authoring surface into codex-rs/tool-api/
• move the shared JSON schema types and parser there as well, and add explicit namespace metadata so bundle authors can describe namespaced tools without depending on host codex-tools types
• keep codex-rs/tools/ as the host owner of Responses API tool specs and code-mode/discovery/MCP/dynamic conversion logic, while re-exporting the shared schema types from codex-tool-api
• update core's extension tool registration path to build host ToolSpecs directly from ToolBundle metadata and coalesce namespaced extension bundles into namespace specs
• update codex_extension_api re-exports and tests to use the new surface

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Do not expose namespace specs when disabled

register_tool_bundle always turns a namespaced extension bundle into ToolSpec::Namespace, but this path is called regardless of config.namespace_tools. MCP and dynamic tools explicitly hide namespace specs when that capability is false; extensions will still be sent in model_visible_specs, causing requests to models without namespace-tool support to fail instead of keeping the handler hidden.

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[jif-oai]

Not sure yet if we need all those accessor but that tends to make my tests cleaner