feat(telemetry): record per-agent usage for mission turns

The command centre's SPEND, ACTIVITY and THROUGHPUT cards read `usage_events`,
and nothing on the mission path ever wrote a row: `cm_billing::charge` was
called only from the agent-run path. Measured mid-mission with 14 agents live,
`usage_events` was 0 while a crew had just burned 15k tokens — so an agent that
had done real work reported zero cost and zero activity.

The worker already knew everything needed: it logs node, role and token count
per step, and the node's `attrs.agent` carries the `claw_<uuid>` binding the
runtime dispatches on. This routes that to the ledger.

`charge`'s run_id is now Option. `usage_events.run_id` references `agent_runs`,
and a topology turn has no row there — passing its `topology_runs` id was a
foreign-key violation, which is exactly what the first attempt hit. NULL is the
honest value; the agent-run caller still passes its real id.

The executor reports one total rather than an in/out split, so the cost is right
(credits price the sum) and the columns record it as output rather than
inventing a split.

Verified end to end on a real mission: 4 agents, 1046-8670 tokens each, credits
attributed per agent, and the SPEND/ACTIVITY queries now return real numbers.

Co-Authored-By: Claude Opus 5 <[email protected]>

crates/cm-runtime/src/runtime.rs

@@ -879,7 +879,7 @@ impl Runtime {
             &self.inner.pool,
             state.workspace_id,
             state.agent_id,
-            run_id,
+            Some(run_id),
             state.input_tokens,
             state.output_tokens,
         )