refactor: add ToolArrayMapper base class for tool-type parameters

[Kamilbenkirane]

Summary

Three parameter mappers in the OpenResponses protocol follow the identical pattern of appending a tool type to the request tools array.

Current Code (repeated 3 times)

class WebSearchMapper(ParameterMapper):
    """Map web_search to Responses tools array."""

    def map(self, request: dict[str, Any], value: object, model: Model) -> dict[str, Any]:
        validated_value = self._validate_value(value, model)
        if not validated_value:
            return request
        request.setdefault("tools", []).append({"type": "web_search"})  # only this differs
        return request

Duplicated for: WebSearchMapper, XSearchMapper, CodeExecutionMapper.

Proposed Change

Add ToolArrayMapper to src/celeste/parameters.py:

class ToolArrayMapper(ParameterMapper):
    """Appends a tool entry to the request tools array."""
    tool_type: str

    def map(self, request: dict[str, Any], value: Any, model: Model) -> dict[str, Any]:
        validated_value = self._validate_value(value, model)
        if not validated_value:
            return request
        request.setdefault("tools", []).append({"type": self.tool_type})
        return request

Each tool mapper becomes:

class WebSearchMapper(ToolArrayMapper):
    tool_type = "web_search"

class XSearchMapper(ToolArrayMapper):
    tool_type = "x_search"

class CodeExecutionMapper(ToolArrayMapper):
    tool_type = "code_execution"

Files to Modify

• src/celeste/parameters.py (add ToolArrayMapper)
• src/celeste/protocols/openresponses/parameters.py (WebSearchMapper, XSearchMapper, CodeExecutionMapper)

Rationale

3 identical 8-line implementations reduced to 3 two-line declarations. If more tools are added (likely, given the OpenResponses API's tool model), they're trivial to add.

[Kamilbenkirane]

Closing this — the three OpenResponses tool mappers (WebSearchMapper, XSearchMapper, CodeExecutionMapper) will be reworked as part of #150 (First-Class Function Calling), which introduces a unified ToolsMapper abstraction across all providers. Extracting ToolArrayMapper now would create a short-lived abstraction that #150 would immediately supersede.