responses: support namespace tool calls

[pd95]

Motivation

The Responses API can group tools under a namespace and represents the
namespace and function name as separate fields. Ollama's internal chat API has
only a flat function name. Passing namespaced tools through without an
injective mapping either loses the namespace on output or makes two children
with the same name ambiguous.

That prevents clients using namespaced tool collections from reliably
round-tripping calls through Ollama's /v1/responses endpoint, especially when
static tools, deferred tool search, prior history, and streamed output are used
together.

What this changes

• maps every external (namespace, name) pair to a unique internal name;
• restores the exact namespace and child name on Responses output;
• applies the same resolver to streaming, non-streaming, and tool-call history;
• preserves explicit flat tools when an internal name would otherwise collide;
• canonicalizes unqualified aliases instead of selecting an ambiguous tool;
• retains Ollama's existing deferred tool-search behavior.

Dependency and scope

This PR is layered after the MLX build fix but is otherwise a standalone
Responses API change with no model-runtime dependency.

Compare:
fix/mlx-external-reconfigure...feature/responses-namespace-tools-upstream

It transports namespace identity only. It does not add custom/freeform tools,
execute tools, or change cached-token accounting.

Validation

Namespace collision, round-trip, tool-search, history, and literal streaming
and non-streaming middleware tests pass. The integrated Linux test/lint/build
and Darwin MLX build gates also pass.

Refresh and AI assistance

Adapted onto Ollama v0.34.0; head
c53c2ebe046e20eec8271b50ab727234ddab1efa. Codex materially assisted the
implementation review, tests, refresh validation, and this PR description.

[pd95]

Closing because GitHub prevents retargeting this stack-managed PR across the two new v0.34.1 Darwin build layers. A replacement follows on the same head branch.

[pd95]

Superseded by #32.