* fix(tools): wire ActivatedToolSet into tool dispatch and spec advertisement
When deferred MCP tools are activated via tool_search, they are stored
in ActivatedToolSet but never consulted by the tool call loop.
tool_specs is built once before the iteration loop and never refreshed,
so the provider API tools[] parameter never includes activated tools.
find_tool only searches the static registry, so execution dispatch also
fails silently.
Thread Arc<Mutex<ActivatedToolSet>> from creation sites through to
run_tool_call_loop. Rebuild tool_specs each iteration to merge base
registry specs with activated specs. Add fallback in execute_one_tool
to check the activated set when the static registry lookup misses.
Change ActivatedToolSet internal storage from Box<dyn Tool> to
Arc<dyn Tool> so we can clone the Arc out of the mutex guard before
awaiting tool.execute() (std::sync::MutexGuard is not Send).
* fix(tools): add activated_tools field to new ChannelRuntimeContext test site
Ricardo Madriz
9a073fae1a