Improve mock agent runner design

[vuchau0802]

Pseudocode — Mock Agent Runner (email_summarizer)

function run_agent(agent_id, user_input):

start timer
generate run_id
initialize empty trace list
initialize empty outputs dict

if agent_id != "email_summarizer":
    return error response

# Step 1 — Build tool chain
chain = email_chain(user_input, prev_outputs={})

# Step 2 — Execute tools in order
for each (tool_id, _) in chain:

    # Rebuild chain with updated outputs
    refreshed_chain = email_chain(user_input, prev_outputs=outputs)
    current_kwargs = refreshed_chain[current_step].kwargs

    # Step 3 — Call mock tool
    tool_fn = TOOL_DISPATCH[tool_id]
    tool_output = tool_fn(**current_kwargs)

    # Step 4 — Record trace step
    trace.append({
        step: index,
        tool_id: tool_id,
        input: current_kwargs,
        output: tool_output,
        status: "success",
        latency_ms: simulated_latency()
    })

    # Save output for next tool
    outputs[tool_id] = tool_output

# Step 5 — Build final output
final_output = build_final_output(agent_id, outputs)

# Step 6 — Save run history to traces/
save_trace(run_id, agent_id, trace, final_output)

return {
    run_id,
    agent_id,
    user_input,
    final_output,
    status: "success",
    trace,
    duration_ms: elapsed_time()
}