`src/middleware/tool_call.rs` — the pipeline core layer

The innermost middleware: performs the registry lookup and runs the tool. No next — it is the end of the chain.

Key items

• ToolCallMiddleware::new(registry) — stored as Arc<ToolRegistry>; name "tool_call".

Behavior notes

• Registry miss → soft error Tool not found: x. Available: ... (the shape UnknownToolMiddleware detects to append suggestions).
• Panic containment: AssertUnwindSafe(tool.call(...)).catch_unwind() raced against cancel; a panic becomes a soft error naming the tool and message — the pipeline never hard-fails from a tool panic.
• Cancellation observed here becomes a soft "tool 'x' cancelled" result — but the engine’s biased cancel-vs-dispatch select usually wins first and surfaces the hard LoopError::Cancelled.

Deep dive: Middleware.