Local LLM adapter: tool-call loop

Adds OpenAI-style tool support to the local Ollama adapter. The
adapter now forwards the caller's tool schemas, assembles tool_calls
from the streamed delta chunks (deltas arrive keyed by index with
arguments streaming in fragments), and runs them via the supplied
runTools callback. Tool results are appended as role=tool messages
with tool_call_id and the loop re-streams until the model produces
content with no further tool calls or maxIterations is hit.

Models that do not support tools simply never emit tool_calls, so
the loop exits after the first turn. Unparseable JSON arguments are
passed through under _raw_arguments rather than crashing the turn.