feat(billing): agent-side spend records who was paid

Judge spend gained provider, model and mission on 2026-09-14; agent spend —
the larger half — did not. The runtime's `done` frame has always carried
`model` and `provider` beside the two token counts, and `topology_exec` read
only the counts, summed them, and charged the sum as output with no record of
which provider served the turn.

`TurnOutcome` and `StepRecord` carry a `Spend` now (input/output split,
provider, model), the worker passes it through `cm_billing::charge` along with
the mission id, and the chat runtime records the model it requested — that
loop drives one provider with no chain, so requested is answered. A bare
model name is recorded without a guessed family. `StepRecord.spend` is
`serde(default)` so journaled checkpoints from before this field still load,
and `tokens` stays as the total every reader keys on.

`charge` moved from `query!` to `query`: the macro pins the statement to
offline metadata that a schema change then has to regenerate against a live
database, for columns that are nullable text and uuid.

The done-frame test now asserts the split and the provider survive, not just
the sum.

Co-Authored-By: Claude Opus 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01WZb5A2kfVfjpdwSochkuHz

crates/cm-runtime/src/runtime.rs

@@ -875,6 +875,13 @@ impl Runtime {
         );
         // Meter the run (§8.4). Billing failures never fail the run — the
         // usage ledger is the recovery path.
+        // This loop drives ONE provider with no fallback chain, so the model
+        // the request named is the model that answered. The family is taken
+        // only from an explicit `provider:` prefix — a bare model name is
+        // recorded as-is with no family rather than guessed at, and a chat
+        // run is not a mission.
+        let model = state.request.model.as_str();
+        let provider = model.split_once(':').map(|(p, _)| p);
         if let Err(error) = cm_billing::charge(
             &self.inner.pool,
             state.workspace_id,
@@ -882,6 +889,9 @@ impl Runtime {
             Some(run_id),
             state.input_tokens,
             state.output_tokens,
+            provider,
+            Some(model),
+            None,
         )
         .await
         {