## Why
MCP tool parsing eagerly cloned structured output schemas and built full call-result envelopes. Cloning tool definitions also copied their output-schema JSON, even before a consumer needed it.
## What changed
- Introduce `ToolOutputSchema` with immutable `Arc` storage so tool definitions share output schemas when cloned.
- Retain MCP structured output schemas and materialize the call-result envelope only when JSON is requested.
- Update code-mode consumers and schema mutation sites to materialize JSON explicitly, reusing uniquely owned storage when possible.
- Move structured content into the MCP envelope without an extra clone, preserving property order.
## Testing
Add tests for JSON preservation, mutation isolation, equality between lazy and materialized schemas, reuse of uniquely owned storage, and equivalent code-mode definitions.
GitOrigin-RevId: e98ba4c2f0efedc99f7cbc7bba206cc63a3bd8f4
## Why
This continues the `codex-tools` migration by moving one more piece of
generic tool-definition bookkeeping out of `codex-core`.
The earlier extraction steps moved shared schema parsing into
`codex-tools`, but `core/src/tools/spec.rs` still had to supply tool
names separately and perform ad hoc rewrites for deferred MCP aliases.
That meant the crate boundary was still awkward: the parsed shape coming
back from `codex-tools` was missing part of the definition that
`codex-core` ultimately needs to assemble a `ResponsesApiTool`.
This change introduces a named `ToolDefinition` in `codex-tools` so both
MCP tools and dynamic tools cross the crate boundary in the same
reusable model. `codex-core` still owns the final `ResponsesApiTool`
assembly, but less of the generic tool-definition shaping logic stays
behind in `core`.
## What changed
- replaced `ParsedToolDefinition` with a named `ToolDefinition` in
`codex-rs/tools/src/tool_definition.rs`
- added `codex-rs/tools/src/tool_definition_tests.rs` for `renamed()`
and `into_deferred()`
- updated `parse_dynamic_tool()` and `parse_mcp_tool()` to return
`ToolDefinition`
- simplified `codex-rs/core/src/tools/spec.rs` so it adapts
`ToolDefinition` into `ResponsesApiTool` instead of rewriting names and
deferred fields inline
- updated parser tests and `codex-rs/tools/README.md` to reflect the
named tool-definition model
## Test plan
- `cargo test -p codex-tools`
- `cargo test -p codex-core --lib tools::spec::`
Charlie Marsh