`src/middleware/timeout.rs` — `TimeoutMiddleware`

A per-call deadline around everything inside it.

Key items

• TimeoutConfig { timeout: 2 min, retry_on_timeout: false, max_retries: 0 }.
• Constructors: new(config), from_secs(u64) (keeps default retry settings), none() (pass-through).

Behavior notes

• On timeout: soft error "Tool 'x' timed out after Ns" — the in-flight future is dropped, no partial output; the reported duration is the configured deadline that expired, not wall time.
• With retries enabled the deadline doubles per attempt; total attempts = 1 + max_retries.
• The wait races the cancel signal — cancellation beats the clock.
• Mutates nothing in the context; preserves the inner result untouched on success.

Deep dive: Middleware.