Op interpreter: correct iteration numbers

Fix iteration tracking in Sequential interpreter.

Problem

SeqConfig.seqIteration never changes, so trace events always report iteration 0. This breaks observability and any iteration-based limits/diagnostics.

Requirements

• Increment iteration per infer cycle
• Emit correct iteration numbers in trace events
• Keep consistent with AgentState.asIteration

Acceptance

• Trace events show increasing iteration values across loops
• watch/status reflect correct iteration counts